• Home
  • Annotate
  • current directory
Name Date Size #Lines LOC

..03-Jun-2023-

Licenses/18-Mar-2022-

api/18-Mar-2022-

common/18-Mar-2022-

configs/18-Mar-2022-

disk/18-Mar-2022-

doc/18-Mar-2022-

dts/18-Mar-2022-

env/18-Mar-2022-

lib/18-Mar-2022-

.git A D01-Jan-19700

.github/18-Mar-2022-

arch/18-Mar-2022-

board/18-Mar-2022-

cmd/18-Mar-2022-

drivers/18-Mar-2022-

examples/18-Mar-2022-

fs/18-Mar-2022-

include/18-Mar-2022-

net/18-Mar-2022-

post/18-Mar-2022-

scripts/18-Mar-2022-

test/18-Mar-2022-

tools/18-Mar-2022-

.azure-pipelines.yml A D18-Mar-202216.6 KiB470456

.checkpatch.conf A D18-Mar-2022720 3411

.gitattributes A D18-Mar-2022169 65

.gitignore A D18-Mar-2022939 9884

.gitlab-ci.yml A D18-Mar-202211.1 KiB416366

.mailmap A D18-Mar-20222.3 KiB5452

.readthedocs.yml A D18-Mar-2022502 2015

Kbuild A D18-Mar-2022737 3020

Kconfig A D18-Mar-202214.8 KiB461389

MAINTAINERS A D18-Mar-202231.6 KiB1,2051,092

Makefile A D18-Mar-202273.1 KiB2,2301,580

README A D18-Mar-2022160.4 KiB4,6243,560

config.mk A D18-Mar-20222.1 KiB7949

README

1# SPDX-License-Identifier: GPL-2.0+
2#
3# (C) Copyright 2000 - 2013
4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5
6Summary:
7========
8
9This directory contains the source code for U-Boot, a boot loader for
10Embedded boards based on PowerPC, ARM, MIPS and several other
11processors, which can be installed in a boot ROM and used to
12initialize and test the hardware or to download and run application
13code.
14
15The development of U-Boot is closely related to Linux: some parts of
16the source code originate in the Linux source tree, we have some
17header files in common, and special provision has been made to
18support booting of Linux images.
19
20Some attention has been paid to make this software easily
21configurable and extendable. For instance, all monitor commands are
22implemented with the same call interface, so that it's very easy to
23add new commands. Also, instead of permanently adding rarely used
24code (for instance hardware test utilities) to the monitor, you can
25load and run it dynamically.
26
27
28Status:
29=======
30
31In general, all boards for which a configuration option exists in the
32Makefile have been tested to some extent and can be considered
33"working". In fact, many of them are used in production systems.
34
35In case of problems see the CHANGELOG file to find out who contributed
36the specific port. In addition, there are various MAINTAINERS files
37scattered throughout the U-Boot source identifying the people or
38companies responsible for various boards and subsystems.
39
40Note: As of August, 2010, there is no longer a CHANGELOG file in the
41actual U-Boot source tree; however, it can be created dynamically
42from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot, you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see https://lists.denx.de/pipermail/u-boot and
55https://marc.info/?l=u-boot
56
57Where to get source code:
58=========================
59
60The U-Boot source code is maintained in the Git repository at
61https://source.denx.de/u-boot/u-boot.git ; you can browse it online at
62https://source.denx.de/u-boot/u-boot
63
64The "Tags" links on this page allow you to download tarballs of
65any version you might be interested in. Official releases are also
66available from the DENX file server through HTTPS or FTP.
67https://ftp.denx.de/pub/u-boot/
68ftp://ftp.denx.de/pub/u-boot/
69
70
71Where we come from:
72===================
73
74- start from 8xxrom sources
75- create PPCBoot project (https://sourceforge.net/projects/ppcboot)
76- clean up code
77- make it easier to add custom boards
78- make it possible to add other [PowerPC] CPUs
79- extend functions, especially:
80  * Provide extended interface to Linux boot loader
81  * S-Record download
82  * network boot
83  * ATA disk / SCSI ... boot
84- create ARMBoot project (https://sourceforge.net/projects/armboot)
85- add other CPU families (starting with ARM)
86- create U-Boot project (https://sourceforge.net/projects/u-boot)
87- current project page: see https://www.denx.de/wiki/U-Boot
88
89
90Names and Spelling:
91===================
92
93The "official" name of this project is "Das U-Boot". The spelling
94"U-Boot" shall be used in all written text (documentation, comments
95in source files etc.). Example:
96
97	This is the README file for the U-Boot project.
98
99File names etc. shall be based on the string "u-boot". Examples:
100
101	include/asm-ppc/u-boot.h
102
103	#include <asm/u-boot.h>
104
105Variable names, preprocessor constants etc. shall be either based on
106the string "u_boot" or on "U_BOOT". Example:
107
108	U_BOOT_VERSION		u_boot_logo
109	IH_OS_U_BOOT		u_boot_hush_start
110
111
112Versioning:
113===========
114
115Starting with the release in October 2008, the names of the releases
116were changed from numerical release numbers without deeper meaning
117into a time stamp based numbering. Regular releases are identified by
118names consisting of the calendar year and month of the release date.
119Additional fields (if present) indicate release candidates or bug fix
120releases in "stable" maintenance trees.
121
122Examples:
123	U-Boot v2009.11	    - Release November 2009
124	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
125	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
126
127
128Directory Hierarchy:
129====================
130
131/arch			Architecture specific files
132  /arc			Files generic to ARC architecture
133  /arm			Files generic to ARM architecture
134  /m68k			Files generic to m68k architecture
135  /microblaze		Files generic to microblaze architecture
136  /mips			Files generic to MIPS architecture
137  /nds32		Files generic to NDS32 architecture
138  /nios2		Files generic to Altera NIOS2 architecture
139  /powerpc		Files generic to PowerPC architecture
140  /riscv		Files generic to RISC-V architecture
141  /sandbox		Files generic to HW-independent "sandbox"
142  /sh			Files generic to SH architecture
143  /x86			Files generic to x86 architecture
144  /xtensa		Files generic to Xtensa architecture
145/api			Machine/arch independent API for external apps
146/board			Board dependent files
147/cmd			U-Boot commands functions
148/common			Misc architecture independent functions
149/configs		Board default configuration files
150/disk			Code for disk drive partition handling
151/doc			Documentation (don't expect too much)
152/drivers		Commonly used device drivers
153/dts			Contains Makefile for building internal U-Boot fdt.
154/env			Environment files
155/examples		Example code for standalone applications, etc.
156/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
157/include		Header Files
158/lib			Library routines generic to all architectures
159/Licenses		Various license files
160/net			Networking code
161/post			Power On Self Test
162/scripts		Various build scripts and Makefiles
163/test			Various unit test files
164/tools			Tools to build S-Record or U-Boot images, etc.
165
166Software Configuration:
167=======================
168
169Configuration is usually done using C preprocessor defines; the
170rationale behind that is to avoid dead code whenever possible.
171
172There are two classes of configuration variables:
173
174* Configuration _OPTIONS_:
175  These are selectable by the user and have names beginning with
176  "CONFIG_".
177
178* Configuration _SETTINGS_:
179  These depend on the hardware etc. and should not be meddled with if
180  you don't know what you're doing; they have names beginning with
181  "CONFIG_SYS_".
182
183Previously, all configuration was done by hand, which involved creating
184symbolic links and editing configuration files manually. More recently,
185U-Boot has added the Kbuild infrastructure used by the Linux kernel,
186allowing you to use the "make menuconfig" command to configure your
187build.
188
189
190Selection of Processor Architecture and Board Type:
191---------------------------------------------------
192
193For all supported boards there are ready-to-use default
194configurations available; just type "make <board_name>_defconfig".
195
196Example: For a TQM823L module type:
197
198	cd u-boot
199	make TQM823L_defconfig
200
201Note: If you're looking for the default configuration file for a board
202you're sure used to be there but is now missing, check the file
203doc/README.scrapyard for a list of no longer supported boards.
204
205Sandbox Environment:
206--------------------
207
208U-Boot can be built natively to run on a Linux host using the 'sandbox'
209board. This allows feature development which is not board- or architecture-
210specific to be undertaken on a native platform. The sandbox is also used to
211run some of U-Boot's tests.
212
213See doc/arch/sandbox.rst for more details.
214
215
216Board Initialisation Flow:
217--------------------------
218
219This is the intended start-up flow for boards. This should apply for both
220SPL and U-Boot proper (i.e. they both follow the same rules).
221
222Note: "SPL" stands for "Secondary Program Loader," which is explained in
223more detail later in this file.
224
225At present, SPL mostly uses a separate code path, but the function names
226and roles of each function are the same. Some boards or architectures
227may not conform to this.  At least most ARM boards which use
228CONFIG_SPL_FRAMEWORK conform to this.
229
230Execution typically starts with an architecture-specific (and possibly
231CPU-specific) start.S file, such as:
232
233	- arch/arm/cpu/armv7/start.S
234	- arch/powerpc/cpu/mpc83xx/start.S
235	- arch/mips/cpu/start.S
236
237and so on. From there, three functions are called; the purpose and
238limitations of each of these functions are described below.
239
240lowlevel_init():
241	- purpose: essential init to permit execution to reach board_init_f()
242	- no global_data or BSS
243	- there is no stack (ARMv7 may have one but it will soon be removed)
244	- must not set up SDRAM or use console
245	- must only do the bare minimum to allow execution to continue to
246		board_init_f()
247	- this is almost never needed
248	- return normally from this function
249
250board_init_f():
251	- purpose: set up the machine ready for running board_init_r():
252		i.e. SDRAM and serial UART
253	- global_data is available
254	- stack is in SRAM
255	- BSS is not available, so you cannot use global/static variables,
256		only stack variables and global_data
257
258	Non-SPL-specific notes:
259	- dram_init() is called to set up DRAM. If already done in SPL this
260		can do nothing
261
262	SPL-specific notes:
263	- you can override the entire board_init_f() function with your own
264		version as needed.
265	- preloader_console_init() can be called here in extremis
266	- should set up SDRAM, and anything needed to make the UART work
267	- there is no need to clear BSS, it will be done by crt0.S
268	- for specific scenarios on certain architectures an early BSS *can*
269	  be made available (via CONFIG_SPL_EARLY_BSS by moving the clearing
270	  of BSS prior to entering board_init_f()) but doing so is discouraged.
271	  Instead it is strongly recommended to architect any code changes
272	  or additions such to not depend on the availability of BSS during
273	  board_init_f() as indicated in other sections of this README to
274	  maintain compatibility and consistency across the entire code base.
275	- must return normally from this function (don't call board_init_r()
276		directly)
277
278Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
279this point the stack and global_data are relocated to below
280CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
281memory.
282
283board_init_r():
284	- purpose: main execution, common code
285	- global_data is available
286	- SDRAM is available
287	- BSS is available, all static/global variables can be used
288	- execution eventually continues to main_loop()
289
290	Non-SPL-specific notes:
291	- U-Boot is relocated to the top of memory and is now running from
292		there.
293
294	SPL-specific notes:
295	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
296		CONFIG_SPL_STACK_R_ADDR points into SDRAM
297	- preloader_console_init() can be called here - typically this is
298		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
299		spl_board_init() function containing this call
300	- loads U-Boot or (in falcon mode) Linux
301
302
303
304Configuration Options:
305----------------------
306
307Configuration depends on the combination of board and CPU type; all
308such information is kept in a configuration file
309"include/configs/<board_name>.h".
310
311Example: For a TQM823L module, all configuration settings are in
312"include/configs/TQM823L.h".
313
314
315Many of the options are named exactly as the corresponding Linux
316kernel configuration options. The intention is to make it easier to
317build a config tool - later.
318
319- ARM Platform Bus Type(CCI):
320		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
321		provides full cache coherency between two clusters of multi-core
322		CPUs and I/O coherency for devices and I/O masters
323
324		CONFIG_SYS_FSL_HAS_CCI400
325
326		Defined For SoC that has cache coherent interconnect
327		CCN-400
328
329		CONFIG_SYS_FSL_HAS_CCN504
330
331		Defined for SoC that has cache coherent interconnect CCN-504
332
333The following options need to be configured:
334
335- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
336
337- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
338
339- 85xx CPU Options:
340		CONFIG_SYS_PPC64
341
342		Specifies that the core is a 64-bit PowerPC implementation (implements
343		the "64" category of the Power ISA). This is necessary for ePAPR
344		compliance, among other possible reasons.
345
346		CONFIG_SYS_FSL_TBCLK_DIV
347
348		Defines the core time base clock divider ratio compared to the
349		system clock.  On most PQ3 devices this is 8, on newer QorIQ
350		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
351
352		CONFIG_SYS_FSL_PCIE_COMPAT
353
354		Defines the string to utilize when trying to match PCIe device
355		tree nodes for the given platform.
356
357		CONFIG_SYS_FSL_ERRATUM_A004510
358
359		Enables a workaround for erratum A004510.  If set,
360		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
361		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
362
363		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
364		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
365
366		Defines one or two SoC revisions (low 8 bits of SVR)
367		for which the A004510 workaround should be applied.
368
369		The rest of SVR is either not relevant to the decision
370		of whether the erratum is present (e.g. p2040 versus
371		p2041) or is implied by the build target, which controls
372		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
373
374		See Freescale App Note 4493 for more information about
375		this erratum.
376
377		CONFIG_A003399_NOR_WORKAROUND
378		Enables a workaround for IFC erratum A003399. It is only
379		required during NOR boot.
380
381		CONFIG_A008044_WORKAROUND
382		Enables a workaround for T1040/T1042 erratum A008044. It is only
383		required during NAND boot and valid for Rev 1.0 SoC revision
384
385		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
386
387		This is the value to write into CCSR offset 0x18600
388		according to the A004510 workaround.
389
390		CONFIG_SYS_FSL_DSP_DDR_ADDR
391		This value denotes start offset of DDR memory which is
392		connected exclusively to the DSP cores.
393
394		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
395		This value denotes start offset of M2 memory
396		which is directly connected to the DSP core.
397
398		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
399		This value denotes start offset of M3 memory which is directly
400		connected to the DSP core.
401
402		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
403		This value denotes start offset of DSP CCSR space.
404
405		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
406		Single Source Clock is clocking mode present in some of FSL SoC's.
407		In this mode, a single differential clock is used to supply
408		clocks to the sysclock, ddrclock and usbclock.
409
410		CONFIG_SYS_CPC_REINIT_F
411		This CONFIG is defined when the CPC is configured as SRAM at the
412		time of U-Boot entry and is required to be re-initialized.
413
414		CONFIG_DEEP_SLEEP
415		Indicates this SoC supports deep sleep feature. If deep sleep is
416		supported, core will start to execute uboot when wakes up.
417
418- Generic CPU options:
419		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
420
421		Defines the endianess of the CPU. Implementation of those
422		values is arch specific.
423
424		CONFIG_SYS_FSL_DDR
425		Freescale DDR driver in use. This type of DDR controller is
426		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
427		SoCs.
428
429		CONFIG_SYS_FSL_DDR_ADDR
430		Freescale DDR memory-mapped register base.
431
432		CONFIG_SYS_FSL_DDR_EMU
433		Specify emulator support for DDR. Some DDR features such as
434		deskew training are not available.
435
436		CONFIG_SYS_FSL_DDRC_GEN1
437		Freescale DDR1 controller.
438
439		CONFIG_SYS_FSL_DDRC_GEN2
440		Freescale DDR2 controller.
441
442		CONFIG_SYS_FSL_DDRC_GEN3
443		Freescale DDR3 controller.
444
445		CONFIG_SYS_FSL_DDRC_GEN4
446		Freescale DDR4 controller.
447
448		CONFIG_SYS_FSL_DDRC_ARM_GEN3
449		Freescale DDR3 controller for ARM-based SoCs.
450
451		CONFIG_SYS_FSL_DDR1
452		Board config to use DDR1. It can be enabled for SoCs with
453		Freescale DDR1 or DDR2 controllers, depending on the board
454		implemetation.
455
456		CONFIG_SYS_FSL_DDR2
457		Board config to use DDR2. It can be enabled for SoCs with
458		Freescale DDR2 or DDR3 controllers, depending on the board
459		implementation.
460
461		CONFIG_SYS_FSL_DDR3
462		Board config to use DDR3. It can be enabled for SoCs with
463		Freescale DDR3 or DDR3L controllers.
464
465		CONFIG_SYS_FSL_DDR3L
466		Board config to use DDR3L. It can be enabled for SoCs with
467		DDR3L controllers.
468
469		CONFIG_SYS_FSL_DDR4
470		Board config to use DDR4. It can be enabled for SoCs with
471		DDR4 controllers.
472
473		CONFIG_SYS_FSL_IFC_BE
474		Defines the IFC controller register space as Big Endian
475
476		CONFIG_SYS_FSL_IFC_LE
477		Defines the IFC controller register space as Little Endian
478
479		CONFIG_SYS_FSL_IFC_CLK_DIV
480		Defines divider of platform clock(clock input to IFC controller).
481
482		CONFIG_SYS_FSL_LBC_CLK_DIV
483		Defines divider of platform clock(clock input to eLBC controller).
484
485		CONFIG_SYS_FSL_PBL_PBI
486		It enables addition of RCW (Power on reset configuration) in built image.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SYS_FSL_PBL_RCW
490		It adds PBI(pre-boot instructions) commands in u-boot build image.
491		PBI commands can be used to configure SoC before it starts the execution.
492		Please refer doc/README.pblimage for more details
493
494		CONFIG_SYS_FSL_DDR_BE
495		Defines the DDR controller register space as Big Endian
496
497		CONFIG_SYS_FSL_DDR_LE
498		Defines the DDR controller register space as Little Endian
499
500		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
501		Physical address from the view of DDR controllers. It is the
502		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
503		it could be different for ARM SoCs.
504
505		CONFIG_SYS_FSL_DDR_INTLV_256B
506		DDR controller interleaving on 256-byte. This is a special
507		interleaving mode, handled by Dickens for Freescale layerscape
508		SoCs with ARM core.
509
510		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
511		Number of controllers used as main memory.
512
513		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
514		Number of controllers used for other than main memory.
515
516		CONFIG_SYS_FSL_HAS_DP_DDR
517		Defines the SoC has DP-DDR used for DPAA.
518
519		CONFIG_SYS_FSL_SEC_BE
520		Defines the SEC controller register space as Big Endian
521
522		CONFIG_SYS_FSL_SEC_LE
523		Defines the SEC controller register space as Little Endian
524
525- MIPS CPU options:
526		CONFIG_SYS_INIT_SP_OFFSET
527
528		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
529		pointer. This is needed for the temporary stack before
530		relocation.
531
532		CONFIG_XWAY_SWAP_BYTES
533
534		Enable compilation of tools/xway-swap-bytes needed for Lantiq
535		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
536		be swapped if a flash programmer is used.
537
538- ARM options:
539		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
540
541		Select high exception vectors of the ARM core, e.g., do not
542		clear the V bit of the c1 register of CP15.
543
544		COUNTER_FREQUENCY
545		Generic timer clock source frequency.
546
547		COUNTER_FREQUENCY_REAL
548		Generic timer clock source frequency if the real clock is
549		different from COUNTER_FREQUENCY, and can only be determined
550		at run time.
551
552- Tegra SoC options:
553		CONFIG_TEGRA_SUPPORT_NON_SECURE
554
555		Support executing U-Boot in non-secure (NS) mode. Certain
556		impossible actions will be skipped if the CPU is in NS mode,
557		such as ARM architectural timer initialization.
558
559- Linux Kernel Interface:
560		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
561
562		When transferring memsize parameter to Linux, some versions
563		expect it to be in bytes, others in MB.
564		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
565
566		CONFIG_OF_LIBFDT
567
568		New kernel versions are expecting firmware settings to be
569		passed using flattened device trees (based on open firmware
570		concepts).
571
572		CONFIG_OF_LIBFDT
573		 * New libfdt-based support
574		 * Adds the "fdt" command
575		 * The bootm command automatically updates the fdt
576
577		OF_TBCLK - The timebase frequency.
578
579		boards with QUICC Engines require OF_QE to set UCC MAC
580		addresses
581
582		CONFIG_OF_BOARD_SETUP
583
584		Board code has addition modification that it wants to make
585		to the flat device tree before handing it off to the kernel
586
587		CONFIG_OF_SYSTEM_SETUP
588
589		Other code has addition modification that it wants to make
590		to the flat device tree before handing it off to the kernel.
591		This causes ft_system_setup() to be called before booting
592		the kernel.
593
594		CONFIG_OF_IDE_FIXUP
595
596		U-Boot can detect if an IDE device is present or not.
597		If not, and this new config option is activated, U-Boot
598		removes the ATA node from the DTS before booting Linux,
599		so the Linux IDE driver does not probe the device and
600		crash. This is needed for buggy hardware (uc101) where
601		no pull down resistor is connected to the signal IDE5V_DD7.
602
603		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
604
605		This setting is mandatory for all boards that have only one
606		machine type and must be used to specify the machine type
607		number as it appears in the ARM machine registry
608		(see https://www.arm.linux.org.uk/developer/machines/).
609		Only boards that have multiple machine types supported
610		in a single configuration file and the machine type is
611		runtime discoverable, do not have to use this setting.
612
613- vxWorks boot parameters:
614
615		bootvx constructs a valid bootline using the following
616		environments variables: bootdev, bootfile, ipaddr, netmask,
617		serverip, gatewayip, hostname, othbootargs.
618		It loads the vxWorks image pointed bootfile.
619
620		Note: If a "bootargs" environment is defined, it will override
621		the defaults discussed just above.
622
623- Cache Configuration:
624		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
625
626- Cache Configuration for ARM:
627		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
628				      controller
629		CONFIG_SYS_PL310_BASE - Physical base address of PL310
630					controller register space
631
632- Serial Ports:
633		CONFIG_PL010_SERIAL
634
635		Define this if you want support for Amba PrimeCell PL010 UARTs.
636
637		CONFIG_PL011_SERIAL
638
639		Define this if you want support for Amba PrimeCell PL011 UARTs.
640
641		CONFIG_PL011_CLOCK
642
643		If you have Amba PrimeCell PL011 UARTs, set this variable to
644		the clock speed of the UARTs.
645
646		CONFIG_PL01x_PORTS
647
648		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
649		define this to a list of base addresses for each (supported)
650		port. See e.g. include/configs/versatile.h
651
652		CONFIG_SERIAL_HW_FLOW_CONTROL
653
654		Define this variable to enable hw flow control in serial driver.
655		Current user of this option is drivers/serial/nsl16550.c driver
656
657- Autoboot Command:
658		CONFIG_BOOTCOMMAND
659		Only needed when CONFIG_BOOTDELAY is enabled;
660		define a command string that is automatically executed
661		when no character is read on the console interface
662		within "Boot Delay" after reset.
663
664		CONFIG_RAMBOOT and CONFIG_NFSBOOT
665		The value of these goes into the environment as
666		"ramboot" and "nfsboot" respectively, and can be used
667		as a convenience, when switching between booting from
668		RAM and NFS.
669
670- Serial Download Echo Mode:
671		CONFIG_LOADS_ECHO
672		If defined to 1, all characters received during a
673		serial download (using the "loads" command) are
674		echoed back. This might be needed by some terminal
675		emulations (like "cu"), but may as well just take
676		time on others. This setting #define's the initial
677		value of the "loads_echo" environment variable.
678
679- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
680		CONFIG_KGDB_BAUDRATE
681		Select one of the baudrates listed in
682		CONFIG_SYS_BAUDRATE_TABLE, see below.
683
684- Removal of commands
685		If no commands are needed to boot, you can disable
686		CONFIG_CMDLINE to remove them. In this case, the command line
687		will not be available, and when U-Boot wants to execute the
688		boot command (on start-up) it will call board_run_command()
689		instead. This can reduce image size significantly for very
690		simple boot procedures.
691
692- Regular expression support:
693		CONFIG_REGEX
694		If this variable is defined, U-Boot is linked against
695		the SLRE (Super Light Regular Expression) library,
696		which adds regex support to some commands, as for
697		example "env grep" and "setexpr".
698
699- Device tree:
700		CONFIG_OF_CONTROL
701		If this variable is defined, U-Boot will use a device tree
702		to configure its devices, instead of relying on statically
703		compiled #defines in the board file. This option is
704		experimental and only available on a few boards. The device
705		tree is available in the global data as gd->fdt_blob.
706
707		U-Boot needs to get its device tree from somewhere. This can
708		be done using one of the three options below:
709
710		CONFIG_OF_EMBED
711		If this variable is defined, U-Boot will embed a device tree
712		binary in its image. This device tree file should be in the
713		board directory and called <soc>-<board>.dts. The binary file
714		is then picked up in board_init_f() and made available through
715		the global data structure as gd->fdt_blob.
716
717		CONFIG_OF_SEPARATE
718		If this variable is defined, U-Boot will build a device tree
719		binary. It will be called u-boot.dtb. Architecture-specific
720		code will locate it at run-time. Generally this works by:
721
722			cat u-boot.bin u-boot.dtb >image.bin
723
724		and in fact, U-Boot does this for you, creating a file called
725		u-boot-dtb.bin which is useful in the common case. You can
726		still use the individual files if you need something more
727		exotic.
728
729		CONFIG_OF_BOARD
730		If this variable is defined, U-Boot will use the device tree
731		provided by the board at runtime instead of embedding one with
732		the image. Only boards defining board_fdt_blob_setup() support
733		this option (see include/fdtdec.h file).
734
735- Watchdog:
736		CONFIG_WATCHDOG
737		If this variable is defined, it enables watchdog
738		support for the SoC. There must be support in the SoC
739		specific code for a watchdog. For the 8xx
740		CPUs, the SIU Watchdog feature is enabled in the SYPCR
741		register.  When supported for a specific SoC is
742		available, then no further board specific code should
743		be needed to use it.
744
745		CONFIG_HW_WATCHDOG
746		When using a watchdog circuitry external to the used
747		SoC, then define this variable and provide board
748		specific code for the "hw_watchdog_reset" function.
749
750- Real-Time Clock:
751
752		When CONFIG_CMD_DATE is selected, the type of the RTC
753		has to be selected, too. Define exactly one of the
754		following options:
755
756		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
757		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
758		CONFIG_RTC_MC146818	- use MC146818 RTC
759		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
760		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
761		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
762		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
763		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
764		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
765		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
766		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
767		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
768					  RV3029 RTC.
769
770		Note that if the RTC uses I2C, then the I2C interface
771		must also be configured. See I2C Support, below.
772
773- GPIO Support:
774		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
775
776		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
777		chip-ngpio pairs that tell the PCA953X driver the number of
778		pins supported by a particular chip.
779
780		Note that if the GPIO device uses I2C, then the I2C interface
781		must also be configured. See I2C Support, below.
782
783- I/O tracing:
784		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
785		accesses and can checksum them or write a list of them out
786		to memory. See the 'iotrace' command for details. This is
787		useful for testing device drivers since it can confirm that
788		the driver behaves the same way before and after a code
789		change. Currently this is supported on sandbox and arm. To
790		add support for your architecture, add '#include <iotrace.h>'
791		to the bottom of arch/<arch>/include/asm/io.h and test.
792
793		Example output from the 'iotrace stats' command is below.
794		Note that if the trace buffer is exhausted, the checksum will
795		still continue to operate.
796
797			iotrace is enabled
798			Start:  10000000	(buffer start address)
799			Size:   00010000	(buffer size)
800			Offset: 00000120	(current buffer offset)
801			Output: 10000120	(start + offset)
802			Count:  00000018	(number of trace records)
803			CRC32:  9526fb66	(CRC32 of all trace records)
804
805- Timestamp Support:
806
807		When CONFIG_TIMESTAMP is selected, the timestamp
808		(date and time) of an image is printed by image
809		commands like bootm or iminfo. This option is
810		automatically enabled when you select CONFIG_CMD_DATE .
811
812- Partition Labels (disklabels) Supported:
813		Zero or more of the following:
814		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
815		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
816		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
817				       bootloader.  Note 2TB partition limit; see
818				       disk/part_efi.c
819		CONFIG_SCSI) you must configure support for at
820		least one non-MTD partition type as well.
821
822- IDE Reset method:
823		CONFIG_IDE_RESET_ROUTINE - this is defined in several
824		board configurations files but used nowhere!
825
826		CONFIG_IDE_RESET - is this is defined, IDE Reset will
827		be performed by calling the function
828			ide_set_reset(int reset)
829		which has to be defined in a board specific file
830
831- ATAPI Support:
832		CONFIG_ATAPI
833
834		Set this to enable ATAPI support.
835
836- LBA48 Support
837		CONFIG_LBA48
838
839		Set this to enable support for disks larger than 137GB
840		Also look at CONFIG_SYS_64BIT_LBA.
841		Whithout these , LBA48 support uses 32bit variables and will 'only'
842		support disks up to 2.1TB.
843
844		CONFIG_SYS_64BIT_LBA:
845			When enabled, makes the IDE subsystem use 64bit sector addresses.
846			Default is 32bit.
847
848- SCSI Support:
849		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
850		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
851		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
852		maximum numbers of LUNs, SCSI ID's and target
853		devices.
854
855		The environment variable 'scsidevs' is set to the number of
856		SCSI devices found during the last scan.
857
858- NETWORK Support (PCI):
859		CONFIG_E1000
860		Support for Intel 8254x/8257x gigabit chips.
861
862		CONFIG_E1000_SPI
863		Utility code for direct access to the SPI bus on Intel 8257x.
864		This does not do anything useful unless you set at least one
865		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
866
867		CONFIG_E1000_SPI_GENERIC
868		Allow generic access to the SPI bus on the Intel 8257x, for
869		example with the "sspi" command.
870
871		CONFIG_NATSEMI
872		Support for National dp83815 chips.
873
874		CONFIG_NS8382X
875		Support for National dp8382[01] gigabit chips.
876
877- NETWORK Support (other):
878
879		CONFIG_DRIVER_AT91EMAC
880		Support for AT91RM9200 EMAC.
881
882			CONFIG_RMII
883			Define this to use reduced MII inteface
884
885			CONFIG_DRIVER_AT91EMAC_QUIET
886			If this defined, the driver is quiet.
887			The driver doen't show link status messages.
888
889		CONFIG_CALXEDA_XGMAC
890		Support for the Calxeda XGMAC device
891
892		CONFIG_LAN91C96
893		Support for SMSC's LAN91C96 chips.
894
895			CONFIG_LAN91C96_USE_32_BIT
896			Define this to enable 32 bit addressing
897
898		CONFIG_SMC91111
899		Support for SMSC's LAN91C111 chip
900
901			CONFIG_SMC91111_BASE
902			Define this to hold the physical address
903			of the device (I/O space)
904
905			CONFIG_SMC_USE_32_BIT
906			Define this if data bus is 32 bits
907
908			CONFIG_SMC_USE_IOFUNCS
909			Define this to use i/o functions instead of macros
910			(some hardware wont work with macros)
911
912			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
913			Define this if you have more then 3 PHYs.
914
915		CONFIG_FTGMAC100
916		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
917
918			CONFIG_FTGMAC100_EGIGA
919			Define this to use GE link update with gigabit PHY.
920			Define this if FTGMAC100 is connected to gigabit PHY.
921			If your system has 10/100 PHY only, it might not occur
922			wrong behavior. Because PHY usually return timeout or
923			useless data when polling gigabit status and gigabit
924			control registers. This behavior won't affect the
925			correctnessof 10/100 link speed update.
926
927		CONFIG_SH_ETHER
928		Support for Renesas on-chip Ethernet controller
929
930			CONFIG_SH_ETHER_USE_PORT
931			Define the number of ports to be used
932
933			CONFIG_SH_ETHER_PHY_ADDR
934			Define the ETH PHY's address
935
936			CONFIG_SH_ETHER_CACHE_WRITEBACK
937			If this option is set, the driver enables cache flush.
938
939- TPM Support:
940		CONFIG_TPM
941		Support TPM devices.
942
943		CONFIG_TPM_TIS_INFINEON
944		Support for Infineon i2c bus TPM devices. Only one device
945		per system is supported at this time.
946
947			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
948			Define the burst count bytes upper limit
949
950		CONFIG_TPM_ST33ZP24
951		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
952
953			CONFIG_TPM_ST33ZP24_I2C
954			Support for STMicroelectronics ST33ZP24 I2C devices.
955			Requires TPM_ST33ZP24 and I2C.
956
957			CONFIG_TPM_ST33ZP24_SPI
958			Support for STMicroelectronics ST33ZP24 SPI devices.
959			Requires TPM_ST33ZP24 and SPI.
960
961		CONFIG_TPM_ATMEL_TWI
962		Support for Atmel TWI TPM device. Requires I2C support.
963
964		CONFIG_TPM_TIS_LPC
965		Support for generic parallel port TPM devices. Only one device
966		per system is supported at this time.
967
968			CONFIG_TPM_TIS_BASE_ADDRESS
969			Base address where the generic TPM device is mapped
970			to. Contemporary x86 systems usually map it at
971			0xfed40000.
972
973		CONFIG_TPM
974		Define this to enable the TPM support library which provides
975		functional interfaces to some TPM commands.
976		Requires support for a TPM device.
977
978		CONFIG_TPM_AUTH_SESSIONS
979		Define this to enable authorized functions in the TPM library.
980		Requires CONFIG_TPM and CONFIG_SHA1.
981
982- USB Support:
983		At the moment only the UHCI host controller is
984		supported (PIP405, MIP405); define
985		CONFIG_USB_UHCI to enable it.
986		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
987		and define CONFIG_USB_STORAGE to enable the USB
988		storage devices.
989		Note:
990		Supported are USB Keyboards and USB Floppy drives
991		(TEAC FD-05PUB).
992
993		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
994		txfilltuning field in the EHCI controller on reset.
995
996		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
997		HW module registers.
998
999- USB Device:
1000		Define the below if you wish to use the USB console.
1001		Once firmware is rebuilt from a serial console issue the
1002		command "setenv stdin usbtty; setenv stdout usbtty" and
1003		attach your USB cable. The Unix command "dmesg" should print
1004		it has found a new device. The environment variable usbtty
1005		can be set to gserial or cdc_acm to enable your device to
1006		appear to a USB host as a Linux gserial device or a
1007		Common Device Class Abstract Control Model serial device.
1008		If you select usbtty = gserial you should be able to enumerate
1009		a Linux host by
1010		# modprobe usbserial vendor=0xVendorID product=0xProductID
1011		else if using cdc_acm, simply setting the environment
1012		variable usbtty to be cdc_acm should suffice. The following
1013		might be defined in YourBoardName.h
1014
1015			CONFIG_USB_DEVICE
1016			Define this to build a UDC device
1017
1018			CONFIG_USB_TTY
1019			Define this to have a tty type of device available to
1020			talk to the UDC device
1021
1022			CONFIG_USBD_HS
1023			Define this to enable the high speed support for usb
1024			device and usbtty. If this feature is enabled, a routine
1025			int is_usbd_high_speed(void)
1026			also needs to be defined by the driver to dynamically poll
1027			whether the enumeration has succeded at high speed or full
1028			speed.
1029
1030			CONFIG_SYS_CONSOLE_IS_IN_ENV
1031			Define this if you want stdin, stdout &/or stderr to
1032			be set to usbtty.
1033
1034		If you have a USB-IF assigned VendorID then you may wish to
1035		define your own vendor specific values either in BoardName.h
1036		or directly in usbd_vendor_info.h. If you don't define
1037		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1038		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1039		should pretend to be a Linux device to it's target host.
1040
1041			CONFIG_USBD_MANUFACTURER
1042			Define this string as the name of your company for
1043			- CONFIG_USBD_MANUFACTURER "my company"
1044
1045			CONFIG_USBD_PRODUCT_NAME
1046			Define this string as the name of your product
1047			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1048
1049			CONFIG_USBD_VENDORID
1050			Define this as your assigned Vendor ID from the USB
1051			Implementors Forum. This *must* be a genuine Vendor ID
1052			to avoid polluting the USB namespace.
1053			- CONFIG_USBD_VENDORID 0xFFFF
1054
1055			CONFIG_USBD_PRODUCTID
1056			Define this as the unique Product ID
1057			for your device
1058			- CONFIG_USBD_PRODUCTID 0xFFFF
1059
1060- ULPI Layer Support:
1061		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1062		the generic ULPI layer. The generic layer accesses the ULPI PHY
1063		via the platform viewport, so you need both the genric layer and
1064		the viewport enabled. Currently only Chipidea/ARC based
1065		viewport is supported.
1066		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1067		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1068		If your ULPI phy needs a different reference clock than the
1069		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1070		the appropriate value in Hz.
1071
1072- MMC Support:
1073		The MMC controller on the Intel PXA is supported. To
1074		enable this define CONFIG_MMC. The MMC can be
1075		accessed from the boot prompt by mapping the device
1076		to physical memory similar to flash. Command line is
1077		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1078		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1079
1080		CONFIG_SH_MMCIF
1081		Support for Renesas on-chip MMCIF controller
1082
1083			CONFIG_SH_MMCIF_ADDR
1084			Define the base address of MMCIF registers
1085
1086			CONFIG_SH_MMCIF_CLK
1087			Define the clock frequency for MMCIF
1088
1089- USB Device Firmware Update (DFU) class support:
1090		CONFIG_DFU_OVER_USB
1091		This enables the USB portion of the DFU USB class
1092
1093		CONFIG_DFU_NAND
1094		This enables support for exposing NAND devices via DFU.
1095
1096		CONFIG_DFU_RAM
1097		This enables support for exposing RAM via DFU.
1098		Note: DFU spec refer to non-volatile memory usage, but
1099		allow usages beyond the scope of spec - here RAM usage,
1100		one that would help mostly the developer.
1101
1102		CONFIG_SYS_DFU_DATA_BUF_SIZE
1103		Dfu transfer uses a buffer before writing data to the
1104		raw storage device. Make the size (in bytes) of this buffer
1105		configurable. The size of this buffer is also configurable
1106		through the "dfu_bufsiz" environment variable.
1107
1108		CONFIG_SYS_DFU_MAX_FILE_SIZE
1109		When updating files rather than the raw storage device,
1110		we use a static buffer to copy the file into and then write
1111		the buffer once we've been given the whole file.  Define
1112		this to the maximum filesize (in bytes) for the buffer.
1113		Default is 4 MiB if undefined.
1114
1115		DFU_DEFAULT_POLL_TIMEOUT
1116		Poll timeout [ms], is the timeout a device can send to the
1117		host. The host must wait for this timeout before sending
1118		a subsequent DFU_GET_STATUS request to the device.
1119
1120		DFU_MANIFEST_POLL_TIMEOUT
1121		Poll timeout [ms], which the device sends to the host when
1122		entering dfuMANIFEST state. Host waits this timeout, before
1123		sending again an USB request to the device.
1124
1125- Journaling Flash filesystem support:
1126		CONFIG_JFFS2_NAND
1127		Define these for a default partition on a NAND device
1128
1129		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1130		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1131		Define these for a default partition on a NOR device
1132
1133- Keyboard Support:
1134		See Kconfig help for available keyboard drivers.
1135
1136		CONFIG_KEYBOARD
1137
1138		Define this to enable a custom keyboard support.
1139		This simply calls drv_keyboard_init() which must be
1140		defined in your board-specific files. This option is deprecated
1141		and is only used by novena. For new boards, use driver model
1142		instead.
1143
1144- Video support:
1145		CONFIG_FSL_DIU_FB
1146		Enable the Freescale DIU video driver.	Reference boards for
1147		SOCs that have a DIU should define this macro to enable DIU
1148		support, and should also define these other macros:
1149
1150			CONFIG_SYS_DIU_ADDR
1151			CONFIG_VIDEO
1152			CONFIG_CFB_CONSOLE
1153			CONFIG_VIDEO_SW_CURSOR
1154			CONFIG_VGA_AS_SINGLE_DEVICE
1155			CONFIG_VIDEO_LOGO
1156			CONFIG_VIDEO_BMP_LOGO
1157
1158		The DIU driver will look for the 'video-mode' environment
1159		variable, and if defined, enable the DIU as a console during
1160		boot.  See the documentation file doc/README.video for a
1161		description of this variable.
1162
1163- LCD Support:	CONFIG_LCD
1164
1165		Define this to enable LCD support (for output to LCD
1166		display); also select one of the supported displays
1167		by defining one of these:
1168
1169		CONFIG_ATMEL_LCD:
1170
1171			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1172
1173		CONFIG_NEC_NL6448AC33:
1174
1175			NEC NL6448AC33-18. Active, color, single scan.
1176
1177		CONFIG_NEC_NL6448BC20
1178
1179			NEC NL6448BC20-08. 6.5", 640x480.
1180			Active, color, single scan.
1181
1182		CONFIG_NEC_NL6448BC33_54
1183
1184			NEC NL6448BC33-54. 10.4", 640x480.
1185			Active, color, single scan.
1186
1187		CONFIG_SHARP_16x9
1188
1189			Sharp 320x240. Active, color, single scan.
1190			It isn't 16x9, and I am not sure what it is.
1191
1192		CONFIG_SHARP_LQ64D341
1193
1194			Sharp LQ64D341 display, 640x480.
1195			Active, color, single scan.
1196
1197		CONFIG_HLD1045
1198
1199			HLD1045 display, 640x480.
1200			Active, color, single scan.
1201
1202		CONFIG_OPTREX_BW
1203
1204			Optrex	 CBL50840-2 NF-FW 99 22 M5
1205			or
1206			Hitachi	 LMG6912RPFC-00T
1207			or
1208			Hitachi	 SP14Q002
1209
1210			320x240. Black & white.
1211
1212		CONFIG_LCD_ALIGNMENT
1213
1214		Normally the LCD is page-aligned (typically 4KB). If this is
1215		defined then the LCD will be aligned to this value instead.
1216		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1217		here, since it is cheaper to change data cache settings on
1218		a per-section basis.
1219
1220
1221		CONFIG_LCD_ROTATION
1222
1223		Sometimes, for example if the display is mounted in portrait
1224		mode or even if it's mounted landscape but rotated by 180degree,
1225		we need to rotate our content of the display relative to the
1226		framebuffer, so that user can read the messages which are
1227		printed out.
1228		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1229		initialized with a given rotation from "vl_rot" out of
1230		"vidinfo_t" which is provided by the board specific code.
1231		The value for vl_rot is coded as following (matching to
1232		fbcon=rotate:<n> linux-kernel commandline):
1233		0 = no rotation respectively 0 degree
1234		1 = 90 degree rotation
1235		2 = 180 degree rotation
1236		3 = 270 degree rotation
1237
1238		If CONFIG_LCD_ROTATION is not defined, the console will be
1239		initialized with 0degree rotation.
1240
1241		CONFIG_LCD_BMP_RLE8
1242
1243		Support drawing of RLE8-compressed bitmaps on the LCD.
1244
1245		CONFIG_I2C_EDID
1246
1247		Enables an 'i2c edid' command which can read EDID
1248		information over I2C from an attached LCD display.
1249
1250- MII/PHY support:
1251		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1252
1253		The clock frequency of the MII bus
1254
1255		CONFIG_PHY_RESET_DELAY
1256
1257		Some PHY like Intel LXT971A need extra delay after
1258		reset before any MII register access is possible.
1259		For such PHY, set this option to the usec delay
1260		required. (minimum 300usec for LXT971A)
1261
1262		CONFIG_PHY_CMD_DELAY (ppc4xx)
1263
1264		Some PHY like Intel LXT971A need extra delay after
1265		command issued before MII status register can be read
1266
1267- IP address:
1268		CONFIG_IPADDR
1269
1270		Define a default value for the IP address to use for
1271		the default Ethernet interface, in case this is not
1272		determined through e.g. bootp.
1273		(Environment variable "ipaddr")
1274
1275- Server IP address:
1276		CONFIG_SERVERIP
1277
1278		Defines a default value for the IP address of a TFTP
1279		server to contact when using the "tftboot" command.
1280		(Environment variable "serverip")
1281
1282		CONFIG_KEEP_SERVERADDR
1283
1284		Keeps the server's MAC address, in the env 'serveraddr'
1285		for passing to bootargs (like Linux's netconsole option)
1286
1287- Gateway IP address:
1288		CONFIG_GATEWAYIP
1289
1290		Defines a default value for the IP address of the
1291		default router where packets to other networks are
1292		sent to.
1293		(Environment variable "gatewayip")
1294
1295- Subnet mask:
1296		CONFIG_NETMASK
1297
1298		Defines a default value for the subnet mask (or
1299		routing prefix) which is used to determine if an IP
1300		address belongs to the local subnet or needs to be
1301		forwarded through a router.
1302		(Environment variable "netmask")
1303
1304- BOOTP Recovery Mode:
1305		CONFIG_BOOTP_RANDOM_DELAY
1306
1307		If you have many targets in a network that try to
1308		boot using BOOTP, you may want to avoid that all
1309		systems send out BOOTP requests at precisely the same
1310		moment (which would happen for instance at recovery
1311		from a power failure, when all systems will try to
1312		boot, thus flooding the BOOTP server. Defining
1313		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1314		inserted before sending out BOOTP requests. The
1315		following delays are inserted then:
1316
1317		1st BOOTP request:	delay 0 ... 1 sec
1318		2nd BOOTP request:	delay 0 ... 2 sec
1319		3rd BOOTP request:	delay 0 ... 4 sec
1320		4th and following
1321		BOOTP requests:		delay 0 ... 8 sec
1322
1323		CONFIG_BOOTP_ID_CACHE_SIZE
1324
1325		BOOTP packets are uniquely identified using a 32-bit ID. The
1326		server will copy the ID from client requests to responses and
1327		U-Boot will use this to determine if it is the destination of
1328		an incoming response. Some servers will check that addresses
1329		aren't in use before handing them out (usually using an ARP
1330		ping) and therefore take up to a few hundred milliseconds to
1331		respond. Network congestion may also influence the time it
1332		takes for a response to make it back to the client. If that
1333		time is too long, U-Boot will retransmit requests. In order
1334		to allow earlier responses to still be accepted after these
1335		retransmissions, U-Boot's BOOTP client keeps a small cache of
1336		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1337		cache. The default is to keep IDs for up to four outstanding
1338		requests. Increasing this will allow U-Boot to accept offers
1339		from a BOOTP client in networks with unusually high latency.
1340
1341- DHCP Advanced Options:
1342		You can fine tune the DHCP functionality by defining
1343		CONFIG_BOOTP_* symbols:
1344
1345		CONFIG_BOOTP_NISDOMAIN
1346		CONFIG_BOOTP_BOOTFILESIZE
1347		CONFIG_BOOTP_NTPSERVER
1348		CONFIG_BOOTP_TIMEOFFSET
1349		CONFIG_BOOTP_VENDOREX
1350		CONFIG_BOOTP_MAY_FAIL
1351
1352		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1353		environment variable, not the BOOTP server.
1354
1355		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1356		after the configured retry count, the call will fail
1357		instead of starting over.  This can be used to fail over
1358		to Link-local IP address configuration if the DHCP server
1359		is not available.
1360
1361		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1362
1363		A 32bit value in microseconds for a delay between
1364		receiving a "DHCP Offer" and sending the "DHCP Request".
1365		This fixes a problem with certain DHCP servers that don't
1366		respond 100% of the time to a "DHCP request". E.g. On an
1367		AT91RM9200 processor running at 180MHz, this delay needed
1368		to be *at least* 15,000 usec before a Windows Server 2003
1369		DHCP server would reply 100% of the time. I recommend at
1370		least 50,000 usec to be safe. The alternative is to hope
1371		that one of the retries will be successful but note that
1372		the DHCP timeout and retry process takes a longer than
1373		this delay.
1374
1375 - Link-local IP address negotiation:
1376		Negotiate with other link-local clients on the local network
1377		for an address that doesn't require explicit configuration.
1378		This is especially useful if a DHCP server cannot be guaranteed
1379		to exist in all environments that the device must operate.
1380
1381		See doc/README.link-local for more information.
1382
1383 - MAC address from environment variables
1384
1385		FDT_SEQ_MACADDR_FROM_ENV
1386
1387		Fix-up device tree with MAC addresses fetched sequentially from
1388		environment variables. This config work on assumption that
1389		non-usable ethernet node of device-tree are either not present
1390		or their status has been marked as "disabled".
1391
1392 - CDP Options:
1393		CONFIG_CDP_DEVICE_ID
1394
1395		The device id used in CDP trigger frames.
1396
1397		CONFIG_CDP_DEVICE_ID_PREFIX
1398
1399		A two character string which is prefixed to the MAC address
1400		of the device.
1401
1402		CONFIG_CDP_PORT_ID
1403
1404		A printf format string which contains the ascii name of
1405		the port. Normally is set to "eth%d" which sets
1406		eth0 for the first Ethernet, eth1 for the second etc.
1407
1408		CONFIG_CDP_CAPABILITIES
1409
1410		A 32bit integer which indicates the device capabilities;
1411		0x00000010 for a normal host which does not forwards.
1412
1413		CONFIG_CDP_VERSION
1414
1415		An ascii string containing the version of the software.
1416
1417		CONFIG_CDP_PLATFORM
1418
1419		An ascii string containing the name of the platform.
1420
1421		CONFIG_CDP_TRIGGER
1422
1423		A 32bit integer sent on the trigger.
1424
1425		CONFIG_CDP_POWER_CONSUMPTION
1426
1427		A 16bit integer containing the power consumption of the
1428		device in .1 of milliwatts.
1429
1430		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1431
1432		A byte containing the id of the VLAN.
1433
1434- Status LED:	CONFIG_LED_STATUS
1435
1436		Several configurations allow to display the current
1437		status using a LED. For instance, the LED will blink
1438		fast while running U-Boot code, stop blinking as
1439		soon as a reply to a BOOTP request was received, and
1440		start blinking slow once the Linux kernel is running
1441		(supported by a status LED driver in the Linux
1442		kernel). Defining CONFIG_LED_STATUS enables this
1443		feature in U-Boot.
1444
1445		Additional options:
1446
1447		CONFIG_LED_STATUS_GPIO
1448		The status LED can be connected to a GPIO pin.
1449		In such cases, the gpio_led driver can be used as a
1450		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1451		to include the gpio_led driver in the U-Boot binary.
1452
1453		CONFIG_GPIO_LED_INVERTED_TABLE
1454		Some GPIO connected LEDs may have inverted polarity in which
1455		case the GPIO high value corresponds to LED off state and
1456		GPIO low value corresponds to LED on state.
1457		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1458		with a list of GPIO LEDs that have inverted polarity.
1459
1460- I2C Support:	CONFIG_SYS_I2C
1461
1462		This enable the NEW i2c subsystem, and will allow you to use
1463		i2c commands at the u-boot command line (as long as you set
1464		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1465		    for defining speed and slave address
1466		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1467		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1468		    for defining speed and slave address
1469		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1470		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1471		    for defining speed and slave address
1472		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1473		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1474		    for defining speed and slave address
1475
1476		- drivers/i2c/fsl_i2c.c:
1477		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1478		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1479		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1480		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1481		    bus.
1482		  - If your board supports a second fsl i2c bus, define
1483		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1484		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1485		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1486		    second bus.
1487
1488		- drivers/i2c/tegra_i2c.c:
1489		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1490		  - This driver adds 4 i2c buses with a fix speed from
1491		    100000 and the slave addr 0!
1492
1493		- drivers/i2c/ppc4xx_i2c.c
1494		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1495		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1496		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1497
1498		- drivers/i2c/i2c_mxc.c
1499		  - activate this driver with CONFIG_SYS_I2C_MXC
1500		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1501		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1502		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1503		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1504		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1505		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1506		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1507		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1508		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1509		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1510		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1511		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1512		If those defines are not set, default value is 100000
1513		for speed, and 0 for slave.
1514
1515		- drivers/i2c/rcar_i2c.c:
1516		  - activate this driver with CONFIG_SYS_I2C_RCAR
1517		  - This driver adds 4 i2c buses
1518
1519		- drivers/i2c/sh_i2c.c:
1520		  - activate this driver with CONFIG_SYS_I2C_SH
1521		  - This driver adds from 2 to 5 i2c buses
1522
1523		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1524		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1525		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1526		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1527		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1528		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1529		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1530		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1531		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1532		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1533		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1534
1535		- drivers/i2c/omap24xx_i2c.c
1536		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1537		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1538		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1539		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1540		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1541		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1542		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1543		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1544		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1545		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1546		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1547
1548		- drivers/i2c/s3c24x0_i2c.c:
1549		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1550		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1551		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1552		    with a fix speed from 100000 and the slave addr 0!
1553
1554		- drivers/i2c/ihs_i2c.c
1555		  - activate this driver with CONFIG_SYS_I2C_IHS
1556		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1557		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1558		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1559		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1560		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1561		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1562		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1563		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1564		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1565		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1566		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1567		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1568		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1569		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1570		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1571		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1572		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1573		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1574		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1575		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1576		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1577
1578		additional defines:
1579
1580		CONFIG_SYS_NUM_I2C_BUSES
1581		Hold the number of i2c buses you want to use.
1582
1583		CONFIG_SYS_I2C_DIRECT_BUS
1584		define this, if you don't use i2c muxes on your hardware.
1585		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1586		omit this define.
1587
1588		CONFIG_SYS_I2C_MAX_HOPS
1589		define how many muxes are maximal consecutively connected
1590		on one i2c bus. If you not use i2c muxes, omit this
1591		define.
1592
1593		CONFIG_SYS_I2C_BUSES
1594		hold a list of buses you want to use, only used if
1595		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1596		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1597		CONFIG_SYS_NUM_I2C_BUSES = 9:
1598
1599		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1600					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1601					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1602					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1603					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1604					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1605					{1, {I2C_NULL_HOP}}, \
1606					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1607					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1608					}
1609
1610		which defines
1611			bus 0 on adapter 0 without a mux
1612			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1613			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1614			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1615			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1616			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1617			bus 6 on adapter 1 without a mux
1618			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1619			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1620
1621		If you do not have i2c muxes on your board, omit this define.
1622
1623- Legacy I2C Support:
1624		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1625		then the following macros need to be defined (examples are
1626		from include/configs/lwmon.h):
1627
1628		I2C_INIT
1629
1630		(Optional). Any commands necessary to enable the I2C
1631		controller or configure ports.
1632
1633		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1634
1635		I2C_ACTIVE
1636
1637		The code necessary to make the I2C data line active
1638		(driven).  If the data line is open collector, this
1639		define can be null.
1640
1641		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1642
1643		I2C_TRISTATE
1644
1645		The code necessary to make the I2C data line tri-stated
1646		(inactive).  If the data line is open collector, this
1647		define can be null.
1648
1649		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1650
1651		I2C_READ
1652
1653		Code that returns true if the I2C data line is high,
1654		false if it is low.
1655
1656		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1657
1658		I2C_SDA(bit)
1659
1660		If <bit> is true, sets the I2C data line high. If it
1661		is false, it clears it (low).
1662
1663		eg: #define I2C_SDA(bit) \
1664			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1665			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1666
1667		I2C_SCL(bit)
1668
1669		If <bit> is true, sets the I2C clock line high. If it
1670		is false, it clears it (low).
1671
1672		eg: #define I2C_SCL(bit) \
1673			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1674			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1675
1676		I2C_DELAY
1677
1678		This delay is invoked four times per clock cycle so this
1679		controls the rate of data transfer.  The data rate thus
1680		is 1 / (I2C_DELAY * 4). Often defined to be something
1681		like:
1682
1683		#define I2C_DELAY  udelay(2)
1684
1685		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1686
1687		If your arch supports the generic GPIO framework (asm/gpio.h),
1688		then you may alternatively define the two GPIOs that are to be
1689		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1690		have GPIO-based defaults assigned to them as appropriate.
1691
1692		You should define these to the GPIO value as given directly to
1693		the generic GPIO functions.
1694
1695		CONFIG_SYS_I2C_INIT_BOARD
1696
1697		When a board is reset during an i2c bus transfer
1698		chips might think that the current transfer is still
1699		in progress. On some boards it is possible to access
1700		the i2c SCLK line directly, either by using the
1701		processor pin as a GPIO or by having a second pin
1702		connected to the bus. If this option is defined a
1703		custom i2c_init_board() routine in boards/xxx/board.c
1704		is run early in the boot sequence.
1705
1706		CONFIG_I2C_MULTI_BUS
1707
1708		This option allows the use of multiple I2C buses, each of which
1709		must have a controller.	 At any point in time, only one bus is
1710		active.	 To switch to a different bus, use the 'i2c dev' command.
1711		Note that bus numbering is zero-based.
1712
1713		CONFIG_SYS_I2C_NOPROBES
1714
1715		This option specifies a list of I2C devices that will be skipped
1716		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1717		is set, specify a list of bus-device pairs.  Otherwise, specify
1718		a 1D array of device addresses
1719
1720		e.g.
1721			#undef	CONFIG_I2C_MULTI_BUS
1722			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1723
1724		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1725
1726			#define CONFIG_I2C_MULTI_BUS
1727			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1728
1729		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1730
1731		CONFIG_SYS_SPD_BUS_NUM
1732
1733		If defined, then this indicates the I2C bus number for DDR SPD.
1734		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1735
1736		CONFIG_SYS_RTC_BUS_NUM
1737
1738		If defined, then this indicates the I2C bus number for the RTC.
1739		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1740
1741		CONFIG_SOFT_I2C_READ_REPEATED_START
1742
1743		defining this will force the i2c_read() function in
1744		the soft_i2c driver to perform an I2C repeated start
1745		between writing the address pointer and reading the
1746		data.  If this define is omitted the default behaviour
1747		of doing a stop-start sequence will be used.  Most I2C
1748		devices can use either method, but some require one or
1749		the other.
1750
1751- SPI Support:	CONFIG_SPI
1752
1753		Enables SPI driver (so far only tested with
1754		SPI EEPROM, also an instance works with Crystal A/D and
1755		D/As on the SACSng board)
1756
1757		CONFIG_SOFT_SPI
1758
1759		Enables a software (bit-bang) SPI driver rather than
1760		using hardware support. This is a general purpose
1761		driver that only requires three general I/O port pins
1762		(two outputs, one input) to function. If this is
1763		defined, the board configuration must define several
1764		SPI configuration items (port pins to use, etc). For
1765		an example, see include/configs/sacsng.h.
1766
1767		CONFIG_SYS_SPI_MXC_WAIT
1768		Timeout for waiting until spi transfer completed.
1769		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1770
1771- FPGA Support: CONFIG_FPGA
1772
1773		Enables FPGA subsystem.
1774
1775		CONFIG_FPGA_<vendor>
1776
1777		Enables support for specific chip vendors.
1778		(ALTERA, XILINX)
1779
1780		CONFIG_FPGA_<family>
1781
1782		Enables support for FPGA family.
1783		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1784
1785		CONFIG_FPGA_COUNT
1786
1787		Specify the number of FPGA devices to support.
1788
1789		CONFIG_SYS_FPGA_PROG_FEEDBACK
1790
1791		Enable printing of hash marks during FPGA configuration.
1792
1793		CONFIG_SYS_FPGA_CHECK_BUSY
1794
1795		Enable checks on FPGA configuration interface busy
1796		status by the configuration function. This option
1797		will require a board or device specific function to
1798		be written.
1799
1800		CONFIG_FPGA_DELAY
1801
1802		If defined, a function that provides delays in the FPGA
1803		configuration driver.
1804
1805		CONFIG_SYS_FPGA_CHECK_CTRLC
1806		Allow Control-C to interrupt FPGA configuration
1807
1808		CONFIG_SYS_FPGA_CHECK_ERROR
1809
1810		Check for configuration errors during FPGA bitfile
1811		loading. For example, abort during Virtex II
1812		configuration if the INIT_B line goes low (which
1813		indicated a CRC error).
1814
1815		CONFIG_SYS_FPGA_WAIT_INIT
1816
1817		Maximum time to wait for the INIT_B line to de-assert
1818		after PROB_B has been de-asserted during a Virtex II
1819		FPGA configuration sequence. The default time is 500
1820		ms.
1821
1822		CONFIG_SYS_FPGA_WAIT_BUSY
1823
1824		Maximum time to wait for BUSY to de-assert during
1825		Virtex II FPGA configuration. The default is 5 ms.
1826
1827		CONFIG_SYS_FPGA_WAIT_CONFIG
1828
1829		Time to wait after FPGA configuration. The default is
1830		200 ms.
1831
1832- Configuration Management:
1833
1834		CONFIG_IDENT_STRING
1835
1836		If defined, this string will be added to the U-Boot
1837		version information (U_BOOT_VERSION)
1838
1839- Vendor Parameter Protection:
1840
1841		U-Boot considers the values of the environment
1842		variables "serial#" (Board Serial Number) and
1843		"ethaddr" (Ethernet Address) to be parameters that
1844		are set once by the board vendor / manufacturer, and
1845		protects these variables from casual modification by
1846		the user. Once set, these variables are read-only,
1847		and write or delete attempts are rejected. You can
1848		change this behaviour:
1849
1850		If CONFIG_ENV_OVERWRITE is #defined in your config
1851		file, the write protection for vendor parameters is
1852		completely disabled. Anybody can change or delete
1853		these parameters.
1854
1855		Alternatively, if you define _both_ an ethaddr in the
1856		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
1857		Ethernet address is installed in the environment,
1858		which can be changed exactly ONCE by the user. [The
1859		serial# is unaffected by this, i. e. it remains
1860		read-only.]
1861
1862		The same can be accomplished in a more flexible way
1863		for any variable by configuring the type of access
1864		to allow for those variables in the ".flags" variable
1865		or define CONFIG_ENV_FLAGS_LIST_STATIC.
1866
1867- Protected RAM:
1868		CONFIG_PRAM
1869
1870		Define this variable to enable the reservation of
1871		"protected RAM", i. e. RAM which is not overwritten
1872		by U-Boot. Define CONFIG_PRAM to hold the number of
1873		kB you want to reserve for pRAM. You can overwrite
1874		this default value by defining an environment
1875		variable "pram" to the number of kB you want to
1876		reserve. Note that the board info structure will
1877		still show the full amount of RAM. If pRAM is
1878		reserved, a new environment variable "mem" will
1879		automatically be defined to hold the amount of
1880		remaining RAM in a form that can be passed as boot
1881		argument to Linux, for instance like that:
1882
1883			setenv bootargs ... mem=\${mem}
1884			saveenv
1885
1886		This way you can tell Linux not to use this memory,
1887		either, which results in a memory region that will
1888		not be affected by reboots.
1889
1890		*WARNING* If your board configuration uses automatic
1891		detection of the RAM size, you must make sure that
1892		this memory test is non-destructive. So far, the
1893		following board configurations are known to be
1894		"pRAM-clean":
1895
1896			IVMS8, IVML24, SPD8xx,
1897			HERMES, IP860, RPXlite, LWMON,
1898			FLAGADM
1899
1900- Access to physical memory region (> 4GB)
1901		Some basic support is provided for operations on memory not
1902		normally accessible to U-Boot - e.g. some architectures
1903		support access to more than 4GB of memory on 32-bit
1904		machines using physical address extension or similar.
1905		Define CONFIG_PHYSMEM to access this basic support, which
1906		currently only supports clearing the memory.
1907
1908- Error Recovery:
1909		CONFIG_NET_RETRY_COUNT
1910
1911		This variable defines the number of retries for
1912		network operations like ARP, RARP, TFTP, or BOOTP
1913		before giving up the operation. If not defined, a
1914		default value of 5 is used.
1915
1916		CONFIG_ARP_TIMEOUT
1917
1918		Timeout waiting for an ARP reply in milliseconds.
1919
1920		CONFIG_NFS_TIMEOUT
1921
1922		Timeout in milliseconds used in NFS protocol.
1923		If you encounter "ERROR: Cannot umount" in nfs command,
1924		try longer timeout such as
1925		#define CONFIG_NFS_TIMEOUT 10000UL
1926
1927	Note:
1928
1929		In the current implementation, the local variables
1930		space and global environment variables space are
1931		separated. Local variables are those you define by
1932		simply typing `name=value'. To access a local
1933		variable later on, you have write `$name' or
1934		`${name}'; to execute the contents of a variable
1935		directly type `$name' at the command prompt.
1936
1937		Global environment variables are those you use
1938		setenv/printenv to work with. To run a command stored
1939		in such a variable, you need to use the run command,
1940		and you must not use the '$' sign to access them.
1941
1942		To store commands and special characters in a
1943		variable, please use double quotation marks
1944		surrounding the whole text of the variable, instead
1945		of the backslashes before semicolons and special
1946		symbols.
1947
1948- Command Line Editing and History:
1949		CONFIG_CMDLINE_PS_SUPPORT
1950
1951		Enable support for changing the command prompt string
1952		at run-time. Only static string is supported so far.
1953		The string is obtained from environment variables PS1
1954		and PS2.
1955
1956- Default Environment:
1957		CONFIG_EXTRA_ENV_SETTINGS
1958
1959		Define this to contain any number of null terminated
1960		strings (variable = value pairs) that will be part of
1961		the default environment compiled into the boot image.
1962
1963		For example, place something like this in your
1964		board's config file:
1965
1966		#define CONFIG_EXTRA_ENV_SETTINGS \
1967			"myvar1=value1\0" \
1968			"myvar2=value2\0"
1969
1970		Warning: This method is based on knowledge about the
1971		internal format how the environment is stored by the
1972		U-Boot code. This is NOT an official, exported
1973		interface! Although it is unlikely that this format
1974		will change soon, there is no guarantee either.
1975		You better know what you are doing here.
1976
1977		Note: overly (ab)use of the default environment is
1978		discouraged. Make sure to check other ways to preset
1979		the environment like the "source" command or the
1980		boot command first.
1981
1982		CONFIG_DELAY_ENVIRONMENT
1983
1984		Normally the environment is loaded when the board is
1985		initialised so that it is available to U-Boot. This inhibits
1986		that so that the environment is not available until
1987		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
1988		this is instead controlled by the value of
1989		/config/load-environment.
1990
1991- TFTP Fixed UDP Port:
1992		CONFIG_TFTP_PORT
1993
1994		If this is defined, the environment variable tftpsrcp
1995		is used to supply the TFTP UDP source port value.
1996		If tftpsrcp isn't defined, the normal pseudo-random port
1997		number generator is used.
1998
1999		Also, the environment variable tftpdstp is used to supply
2000		the TFTP UDP destination port value.  If tftpdstp isn't
2001		defined, the normal port 69 is used.
2002
2003		The purpose for tftpsrcp is to allow a TFTP server to
2004		blindly start the TFTP transfer using the pre-configured
2005		target IP address and UDP port. This has the effect of
2006		"punching through" the (Windows XP) firewall, allowing
2007		the remainder of the TFTP transfer to proceed normally.
2008		A better solution is to properly configure the firewall,
2009		but sometimes that is not allowed.
2010
2011		CONFIG_STANDALONE_LOAD_ADDR
2012
2013		This option defines a board specific value for the
2014		address where standalone program gets loaded, thus
2015		overwriting the architecture dependent default
2016		settings.
2017
2018- Frame Buffer Address:
2019		CONFIG_FB_ADDR
2020
2021		Define CONFIG_FB_ADDR if you want to use specific
2022		address for frame buffer.  This is typically the case
2023		when using a graphics controller has separate video
2024		memory.  U-Boot will then place the frame buffer at
2025		the given address instead of dynamically reserving it
2026		in system RAM by calling lcd_setmem(), which grabs
2027		the memory for the frame buffer depending on the
2028		configured panel size.
2029
2030		Please see board_init_f function.
2031
2032- Automatic software updates via TFTP server
2033		CONFIG_UPDATE_TFTP
2034		CONFIG_UPDATE_TFTP_CNT_MAX
2035		CONFIG_UPDATE_TFTP_MSEC_MAX
2036
2037		These options enable and control the auto-update feature;
2038		for a more detailed description refer to doc/README.update.
2039
2040- MTD Support (mtdparts command, UBI support)
2041		CONFIG_MTD_UBI_WL_THRESHOLD
2042		This parameter defines the maximum difference between the highest
2043		erase counter value and the lowest erase counter value of eraseblocks
2044		of UBI devices. When this threshold is exceeded, UBI starts performing
2045		wear leveling by means of moving data from eraseblock with low erase
2046		counter to eraseblocks with high erase counter.
2047
2048		The default value should be OK for SLC NAND flashes, NOR flashes and
2049		other flashes which have eraseblock life-cycle 100000 or more.
2050		However, in case of MLC NAND flashes which typically have eraseblock
2051		life-cycle less than 10000, the threshold should be lessened (e.g.,
2052		to 128 or 256, although it does not have to be power of 2).
2053
2054		default: 4096
2055
2056		CONFIG_MTD_UBI_BEB_LIMIT
2057		This option specifies the maximum bad physical eraseblocks UBI
2058		expects on the MTD device (per 1024 eraseblocks). If the
2059		underlying flash does not admit of bad eraseblocks (e.g. NOR
2060		flash), this value is ignored.
2061
2062		NAND datasheets often specify the minimum and maximum NVM
2063		(Number of Valid Blocks) for the flashes' endurance lifetime.
2064		The maximum expected bad eraseblocks per 1024 eraseblocks
2065		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2066		which gives 20 for most NANDs (MaxNVB is basically the total
2067		count of eraseblocks on the chip).
2068
2069		To put it differently, if this value is 20, UBI will try to
2070		reserve about 1.9% of physical eraseblocks for bad blocks
2071		handling. And that will be 1.9% of eraseblocks on the entire
2072		NAND chip, not just the MTD partition UBI attaches. This means
2073		that if you have, say, a NAND flash chip admits maximum 40 bad
2074		eraseblocks, and it is split on two MTD partitions of the same
2075		size, UBI will reserve 40 eraseblocks when attaching a
2076		partition.
2077
2078		default: 20
2079
2080		CONFIG_MTD_UBI_FASTMAP
2081		Fastmap is a mechanism which allows attaching an UBI device
2082		in nearly constant time. Instead of scanning the whole MTD device it
2083		only has to locate a checkpoint (called fastmap) on the device.
2084		The on-flash fastmap contains all information needed to attach
2085		the device. Using fastmap makes only sense on large devices where
2086		attaching by scanning takes long. UBI will not automatically install
2087		a fastmap on old images, but you can set the UBI parameter
2088		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2089		that fastmap-enabled images are still usable with UBI implementations
2090		without	fastmap support. On typical flash devices the whole fastmap
2091		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2092
2093		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2094		Set this parameter to enable fastmap automatically on images
2095		without a fastmap.
2096		default: 0
2097
2098		CONFIG_MTD_UBI_FM_DEBUG
2099		Enable UBI fastmap debug
2100		default: 0
2101
2102- SPL framework
2103		CONFIG_SPL
2104		Enable building of SPL globally.
2105
2106		CONFIG_SPL_LDSCRIPT
2107		LDSCRIPT for linking the SPL binary.
2108
2109		CONFIG_SPL_MAX_FOOTPRINT
2110		Maximum size in memory allocated to the SPL, BSS included.
2111		When defined, the linker checks that the actual memory
2112		used by SPL from _start to __bss_end does not exceed it.
2113		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2114		must not be both defined at the same time.
2115
2116		CONFIG_SPL_MAX_SIZE
2117		Maximum size of the SPL image (text, data, rodata, and
2118		linker lists sections), BSS excluded.
2119		When defined, the linker checks that the actual size does
2120		not exceed it.
2121
2122		CONFIG_SPL_RELOC_TEXT_BASE
2123		Address to relocate to.  If unspecified, this is equal to
2124		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2125
2126		CONFIG_SPL_BSS_START_ADDR
2127		Link address for the BSS within the SPL binary.
2128
2129		CONFIG_SPL_BSS_MAX_SIZE
2130		Maximum size in memory allocated to the SPL BSS.
2131		When defined, the linker checks that the actual memory used
2132		by SPL from __bss_start to __bss_end does not exceed it.
2133		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2134		must not be both defined at the same time.
2135
2136		CONFIG_SPL_STACK
2137		Adress of the start of the stack SPL will use
2138
2139		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2140		When defined, SPL will panic() if the image it has
2141		loaded does not have a signature.
2142		Defining this is useful when code which loads images
2143		in SPL cannot guarantee that absolutely all read errors
2144		will be caught.
2145		An example is the LPC32XX MLC NAND driver, which will
2146		consider that a completely unreadable NAND block is bad,
2147		and thus should be skipped silently.
2148
2149		CONFIG_SPL_RELOC_STACK
2150		Adress of the start of the stack SPL will use after
2151		relocation.  If unspecified, this is equal to
2152		CONFIG_SPL_STACK.
2153
2154		CONFIG_SYS_SPL_MALLOC_START
2155		Starting address of the malloc pool used in SPL.
2156		When this option is set the full malloc is used in SPL and
2157		it is set up by spl_init() and before that, the simple malloc()
2158		can be used if CONFIG_SYS_MALLOC_F is defined.
2159
2160		CONFIG_SYS_SPL_MALLOC_SIZE
2161		The size of the malloc pool used in SPL.
2162
2163		CONFIG_SPL_OS_BOOT
2164		Enable booting directly to an OS from SPL.
2165		See also: doc/README.falcon
2166
2167		CONFIG_SPL_DISPLAY_PRINT
2168		For ARM, enable an optional function to print more information
2169		about the running system.
2170
2171		CONFIG_SPL_INIT_MINIMAL
2172		Arch init code should be built for a very small image
2173
2174		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2175		Partition on the MMC to load U-Boot from when the MMC is being
2176		used in raw mode
2177
2178		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2179		Sector to load kernel uImage from when MMC is being
2180		used in raw mode (for Falcon mode)
2181
2182		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2183		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2184		Sector and number of sectors to load kernel argument
2185		parameters from when MMC is being used in raw mode
2186		(for falcon mode)
2187
2188		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2189		Filename to read to load U-Boot when reading from filesystem
2190
2191		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2192		Filename to read to load kernel uImage when reading
2193		from filesystem (for Falcon mode)
2194
2195		CONFIG_SPL_FS_LOAD_ARGS_NAME
2196		Filename to read to load kernel argument parameters
2197		when reading from filesystem (for Falcon mode)
2198
2199		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2200		Set this for NAND SPL on PPC mpc83xx targets, so that
2201		start.S waits for the rest of the SPL to load before
2202		continuing (the hardware starts execution after just
2203		loading the first page rather than the full 4K).
2204
2205		CONFIG_SPL_SKIP_RELOCATE
2206		Avoid SPL relocation
2207
2208		CONFIG_SPL_NAND_IDENT
2209		SPL uses the chip ID list to identify the NAND flash.
2210		Requires CONFIG_SPL_NAND_BASE.
2211
2212		CONFIG_SPL_UBI
2213		Support for a lightweight UBI (fastmap) scanner and
2214		loader
2215
2216		CONFIG_SPL_NAND_RAW_ONLY
2217		Support to boot only raw u-boot.bin images. Use this only
2218		if you need to save space.
2219
2220		CONFIG_SPL_COMMON_INIT_DDR
2221		Set for common ddr init with serial presence detect in
2222		SPL binary.
2223
2224		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2225		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2226		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2227		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2228		CONFIG_SYS_NAND_ECCBYTES
2229		Defines the size and behavior of the NAND that SPL uses
2230		to read U-Boot
2231
2232		CONFIG_SYS_NAND_U_BOOT_OFFS
2233		Location in NAND to read U-Boot from
2234
2235		CONFIG_SYS_NAND_U_BOOT_DST
2236		Location in memory to load U-Boot to
2237
2238		CONFIG_SYS_NAND_U_BOOT_SIZE
2239		Size of image to load
2240
2241		CONFIG_SYS_NAND_U_BOOT_START
2242		Entry point in loaded image to jump to
2243
2244		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2245		Define this if you need to first read the OOB and then the
2246		data. This is used, for example, on davinci platforms.
2247
2248		CONFIG_SPL_RAM_DEVICE
2249		Support for running image already present in ram, in SPL binary
2250
2251		CONFIG_SPL_PAD_TO
2252		Image offset to which the SPL should be padded before appending
2253		the SPL payload. By default, this is defined as
2254		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2255		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2256		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2257
2258		CONFIG_SPL_TARGET
2259		Final target image containing SPL and payload.  Some SPLs
2260		use an arch-specific makefile fragment instead, for
2261		example if more than one image needs to be produced.
2262
2263		CONFIG_SPL_FIT_PRINT
2264		Printing information about a FIT image adds quite a bit of
2265		code to SPL. So this is normally disabled in SPL. Use this
2266		option to re-enable it. This will affect the output of the
2267		bootm command when booting a FIT image.
2268
2269- TPL framework
2270		CONFIG_TPL
2271		Enable building of TPL globally.
2272
2273		CONFIG_TPL_PAD_TO
2274		Image offset to which the TPL should be padded before appending
2275		the TPL payload. By default, this is defined as
2276		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2277		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2278		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2279
2280- Interrupt support (PPC):
2281
2282		There are common interrupt_init() and timer_interrupt()
2283		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2284		for CPU specific initialization. interrupt_init_cpu()
2285		should set decrementer_count to appropriate value. If
2286		CPU resets decrementer automatically after interrupt
2287		(ppc4xx) it should set decrementer_count to zero.
2288		timer_interrupt() calls timer_interrupt_cpu() for CPU
2289		specific handling. If board has watchdog / status_led
2290		/ other_activity_monitor it works automatically from
2291		general timer_interrupt().
2292
2293
2294Board initialization settings:
2295------------------------------
2296
2297During Initialization u-boot calls a number of board specific functions
2298to allow the preparation of board specific prerequisites, e.g. pin setup
2299before drivers are initialized. To enable these callbacks the
2300following configuration macros have to be defined. Currently this is
2301architecture specific, so please check arch/your_architecture/lib/board.c
2302typically in board_init_f() and board_init_r().
2303
2304- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2305- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2306- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2307- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2308
2309Configuration Settings:
2310-----------------------
2311
2312- MEM_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2313		Optionally it can be defined to support 64-bit memory commands.
2314
2315- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2316		undefine this when you're short of memory.
2317
2318- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2319		width of the commands listed in the 'help' command output.
2320
2321- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2322		prompt for user input.
2323
2324- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2325
2326- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2327
2328- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2329
2330- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2331		the application (usually a Linux kernel) when it is
2332		booted
2333
2334- CONFIG_SYS_BAUDRATE_TABLE:
2335		List of legal baudrate settings for this board.
2336
2337- CONFIG_SYS_MEM_RESERVE_SECURE
2338		Only implemented for ARMv8 for now.
2339		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2340		is substracted from total RAM and won't be reported to OS.
2341		This memory can be used as secure memory. A variable
2342		gd->arch.secure_ram is used to track the location. In systems
2343		the RAM base is not zero, or RAM is divided into banks,
2344		this variable needs to be recalcuated to get the address.
2345
2346- CONFIG_SYS_MEM_TOP_HIDE:
2347		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2348		this specified memory area will get subtracted from the top
2349		(end) of RAM and won't get "touched" at all by U-Boot. By
2350		fixing up gd->ram_size the Linux kernel should gets passed
2351		the now "corrected" memory size and won't touch it either.
2352		This should work for arch/ppc and arch/powerpc. Only Linux
2353		board ports in arch/powerpc with bootwrapper support that
2354		recalculate the memory size from the SDRAM controller setup
2355		will have to get fixed in Linux additionally.
2356
2357		This option can be used as a workaround for the 440EPx/GRx
2358		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2359		be touched.
2360
2361		WARNING: Please make sure that this value is a multiple of
2362		the Linux page size (normally 4k). If this is not the case,
2363		then the end address of the Linux memory will be located at a
2364		non page size aligned address and this could cause major
2365		problems.
2366
2367- CONFIG_SYS_LOADS_BAUD_CHANGE:
2368		Enable temporary baudrate change while serial download
2369
2370- CONFIG_SYS_SDRAM_BASE:
2371		Physical start address of SDRAM. _Must_ be 0 here.
2372
2373- CONFIG_SYS_FLASH_BASE:
2374		Physical start address of Flash memory.
2375
2376- CONFIG_SYS_MONITOR_BASE:
2377		Physical start address of boot monitor code (set by
2378		make config files to be same as the text base address
2379		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2380		CONFIG_SYS_FLASH_BASE when booting from flash.
2381
2382- CONFIG_SYS_MONITOR_LEN:
2383		Size of memory reserved for monitor code, used to
2384		determine _at_compile_time_ (!) if the environment is
2385		embedded within the U-Boot image, or in a separate
2386		flash sector.
2387
2388- CONFIG_SYS_MALLOC_LEN:
2389		Size of DRAM reserved for malloc() use.
2390
2391- CONFIG_SYS_MALLOC_F_LEN
2392		Size of the malloc() pool for use before relocation. If
2393		this is defined, then a very simple malloc() implementation
2394		will become available before relocation. The address is just
2395		below the global data, and the stack is moved down to make
2396		space.
2397
2398		This feature allocates regions with increasing addresses
2399		within the region. calloc() is supported, but realloc()
2400		is not available. free() is supported but does nothing.
2401		The memory will be freed (or in fact just forgotten) when
2402		U-Boot relocates itself.
2403
2404- CONFIG_SYS_MALLOC_SIMPLE
2405		Provides a simple and small malloc() and calloc() for those
2406		boards which do not use the full malloc in SPL (which is
2407		enabled with CONFIG_SYS_SPL_MALLOC_START).
2408
2409- CONFIG_SYS_NONCACHED_MEMORY:
2410		Size of non-cached memory area. This area of memory will be
2411		typically located right below the malloc() area and mapped
2412		uncached in the MMU. This is useful for drivers that would
2413		otherwise require a lot of explicit cache maintenance. For
2414		some drivers it's also impossible to properly maintain the
2415		cache. For example if the regions that need to be flushed
2416		are not a multiple of the cache-line size, *and* padding
2417		cannot be allocated between the regions to align them (i.e.
2418		if the HW requires a contiguous array of regions, and the
2419		size of each region is not cache-aligned), then a flush of
2420		one region may result in overwriting data that hardware has
2421		written to another region in the same cache-line. This can
2422		happen for example in network drivers where descriptors for
2423		buffers are typically smaller than the CPU cache-line (e.g.
2424		16 bytes vs. 32 or 64 bytes).
2425
2426		Non-cached memory is only supported on 32-bit ARM at present.
2427
2428- CONFIG_SYS_BOOTM_LEN:
2429		Normally compressed uImages are limited to an
2430		uncompressed size of 8 MBytes. If this is not enough,
2431		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2432		to adjust this setting to your needs.
2433
2434- CONFIG_SYS_BOOTMAPSZ:
2435		Maximum size of memory mapped by the startup code of
2436		the Linux kernel; all data that must be processed by
2437		the Linux kernel (bd_info, boot arguments, FDT blob if
2438		used) must be put below this limit, unless "bootm_low"
2439		environment variable is defined and non-zero. In such case
2440		all data for the Linux kernel must be between "bootm_low"
2441		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2442		variable "bootm_mapsize" will override the value of
2443		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2444		then the value in "bootm_size" will be used instead.
2445
2446- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2447		Enable initrd_high functionality.  If defined then the
2448		initrd_high feature is enabled and the bootm ramdisk subcommand
2449		is enabled.
2450
2451- CONFIG_SYS_BOOT_GET_CMDLINE:
2452		Enables allocating and saving kernel cmdline in space between
2453		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2454
2455- CONFIG_SYS_BOOT_GET_KBD:
2456		Enables allocating and saving a kernel copy of the bd_info in
2457		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2458
2459- CONFIG_SYS_MAX_FLASH_BANKS:
2460		Max number of Flash memory banks
2461
2462- CONFIG_SYS_MAX_FLASH_SECT:
2463		Max number of sectors on a Flash chip
2464
2465- CONFIG_SYS_FLASH_ERASE_TOUT:
2466		Timeout for Flash erase operations (in ms)
2467
2468- CONFIG_SYS_FLASH_WRITE_TOUT:
2469		Timeout for Flash write operations (in ms)
2470
2471- CONFIG_SYS_FLASH_LOCK_TOUT
2472		Timeout for Flash set sector lock bit operation (in ms)
2473
2474- CONFIG_SYS_FLASH_UNLOCK_TOUT
2475		Timeout for Flash clear lock bits operation (in ms)
2476
2477- CONFIG_SYS_FLASH_PROTECTION
2478		If defined, hardware flash sectors protection is used
2479		instead of U-Boot software protection.
2480
2481- CONFIG_SYS_DIRECT_FLASH_TFTP:
2482
2483		Enable TFTP transfers directly to flash memory;
2484		without this option such a download has to be
2485		performed in two steps: (1) download to RAM, and (2)
2486		copy from RAM to flash.
2487
2488		The two-step approach is usually more reliable, since
2489		you can check if the download worked before you erase
2490		the flash, but in some situations (when system RAM is
2491		too limited to allow for a temporary copy of the
2492		downloaded image) this option may be very useful.
2493
2494- CONFIG_SYS_FLASH_CFI:
2495		Define if the flash driver uses extra elements in the
2496		common flash structure for storing flash geometry.
2497
2498- CONFIG_FLASH_CFI_DRIVER
2499		This option also enables the building of the cfi_flash driver
2500		in the drivers directory
2501
2502- CONFIG_FLASH_CFI_MTD
2503		This option enables the building of the cfi_mtd driver
2504		in the drivers directory. The driver exports CFI flash
2505		to the MTD layer.
2506
2507- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2508		Use buffered writes to flash.
2509
2510- CONFIG_FLASH_SPANSION_S29WS_N
2511		s29ws-n MirrorBit flash has non-standard addresses for buffered
2512		write commands.
2513
2514- CONFIG_SYS_FLASH_QUIET_TEST
2515		If this option is defined, the common CFI flash doesn't
2516		print it's warning upon not recognized FLASH banks. This
2517		is useful, if some of the configured banks are only
2518		optionally available.
2519
2520- CONFIG_FLASH_SHOW_PROGRESS
2521		If defined (must be an integer), print out countdown
2522		digits and dots.  Recommended value: 45 (9..1) for 80
2523		column displays, 15 (3..1) for 40 column displays.
2524
2525- CONFIG_FLASH_VERIFY
2526		If defined, the content of the flash (destination) is compared
2527		against the source after the write operation. An error message
2528		will be printed when the contents are not identical.
2529		Please note that this option is useless in nearly all cases,
2530		since such flash programming errors usually are detected earlier
2531		while unprotecting/erasing/programming. Please only enable
2532		this option if you really know what you are doing.
2533
2534- CONFIG_SYS_RX_ETH_BUFFER:
2535		Defines the number of Ethernet receive buffers. On some
2536		Ethernet controllers it is recommended to set this value
2537		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2538		buffers can be full shortly after enabling the interface
2539		on high Ethernet traffic.
2540		Defaults to 4 if not defined.
2541
2542- CONFIG_ENV_MAX_ENTRIES
2543
2544	Maximum number of entries in the hash table that is used
2545	internally to store the environment settings. The default
2546	setting is supposed to be generous and should work in most
2547	cases. This setting can be used to tune behaviour; see
2548	lib/hashtable.c for details.
2549
2550- CONFIG_ENV_FLAGS_LIST_DEFAULT
2551- CONFIG_ENV_FLAGS_LIST_STATIC
2552	Enable validation of the values given to environment variables when
2553	calling env set.  Variables can be restricted to only decimal,
2554	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2555	the variables can also be restricted to IP address or MAC address.
2556
2557	The format of the list is:
2558		type_attribute = [s|d|x|b|i|m]
2559		access_attribute = [a|r|o|c]
2560		attributes = type_attribute[access_attribute]
2561		entry = variable_name[:attributes]
2562		list = entry[,list]
2563
2564	The type attributes are:
2565		s - String (default)
2566		d - Decimal
2567		x - Hexadecimal
2568		b - Boolean ([1yYtT|0nNfF])
2569		i - IP address
2570		m - MAC address
2571
2572	The access attributes are:
2573		a - Any (default)
2574		r - Read-only
2575		o - Write-once
2576		c - Change-default
2577
2578	- CONFIG_ENV_FLAGS_LIST_DEFAULT
2579		Define this to a list (string) to define the ".flags"
2580		environment variable in the default or embedded environment.
2581
2582	- CONFIG_ENV_FLAGS_LIST_STATIC
2583		Define this to a list (string) to define validation that
2584		should be done if an entry is not found in the ".flags"
2585		environment variable.  To override a setting in the static
2586		list, simply add an entry for the same variable name to the
2587		".flags" variable.
2588
2589	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
2590	regular expression. This allows multiple variables to define the same
2591	flags without explicitly listing them for each variable.
2592
2593The following definitions that deal with the placement and management
2594of environment data (variable area); in general, we support the
2595following configurations:
2596
2597- CONFIG_BUILD_ENVCRC:
2598
2599	Builds up envcrc with the target environment so that external utils
2600	may easily extract it and embed it in final U-Boot images.
2601
2602BE CAREFUL! The first access to the environment happens quite early
2603in U-Boot initialization (when we try to get the setting of for the
2604console baudrate). You *MUST* have mapped your NVRAM area then, or
2605U-Boot will hang.
2606
2607Please note that even with NVRAM we still use a copy of the
2608environment in RAM: we could work on NVRAM directly, but we want to
2609keep settings there always unmodified except somebody uses "saveenv"
2610to save the current settings.
2611
2612BE CAREFUL! For some special cases, the local device can not use
2613"saveenv" command. For example, the local device will get the
2614environment stored in a remote NOR flash by SRIO or PCIE link,
2615but it can not erase, write this NOR flash by SRIO or PCIE interface.
2616
2617- CONFIG_NAND_ENV_DST
2618
2619	Defines address in RAM to which the nand_spl code should copy the
2620	environment. If redundant environment is used, it will be copied to
2621	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
2622
2623Please note that the environment is read-only until the monitor
2624has been relocated to RAM and a RAM copy of the environment has been
2625created; also, when using EEPROM you will have to use env_get_f()
2626until then to read environment variables.
2627
2628The environment is protected by a CRC32 checksum. Before the monitor
2629is relocated into RAM, as a result of a bad CRC you will be working
2630with the compiled-in default environment - *silently*!!! [This is
2631necessary, because the first environment variable we need is the
2632"baudrate" setting for the console - if we have a bad CRC, we don't
2633have any device yet where we could complain.]
2634
2635Note: once the monitor has been relocated, then it will complain if
2636the default environment is used; a new CRC is computed as soon as you
2637use the "saveenv" command to store a valid environment.
2638
2639- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
2640		Echo the inverted Ethernet link state to the fault LED.
2641
2642		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
2643		      also needs to be defined.
2644
2645- CONFIG_SYS_FAULT_MII_ADDR:
2646		MII address of the PHY to check for the Ethernet link state.
2647
2648- CONFIG_NS16550_MIN_FUNCTIONS:
2649		Define this if you desire to only have use of the NS16550_init
2650		and NS16550_putc functions for the serial driver located at
2651		drivers/serial/ns16550.c.  This option is useful for saving
2652		space for already greatly restricted images, including but not
2653		limited to NAND_SPL configurations.
2654
2655- CONFIG_DISPLAY_BOARDINFO
2656		Display information about the board that U-Boot is running on
2657		when U-Boot starts up. The board function checkboard() is called
2658		to do this.
2659
2660- CONFIG_DISPLAY_BOARDINFO_LATE
2661		Similar to the previous option, but display this information
2662		later, once stdio is running and output goes to the LCD, if
2663		present.
2664
2665- CONFIG_BOARD_SIZE_LIMIT:
2666		Maximum size of the U-Boot image. When defined, the
2667		build system checks that the actual size does not
2668		exceed it.
2669
2670Low Level (hardware related) configuration options:
2671---------------------------------------------------
2672
2673- CONFIG_SYS_CACHELINE_SIZE:
2674		Cache Line Size of the CPU.
2675
2676- CONFIG_SYS_CCSRBAR_DEFAULT:
2677		Default (power-on reset) physical address of CCSR on Freescale
2678		PowerPC SOCs.
2679
2680- CONFIG_SYS_CCSRBAR:
2681		Virtual address of CCSR.  On a 32-bit build, this is typically
2682		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
2683
2684- CONFIG_SYS_CCSRBAR_PHYS:
2685		Physical address of CCSR.  CCSR can be relocated to a new
2686		physical address, if desired.  In this case, this macro should
2687		be set to that address.	 Otherwise, it should be set to the
2688		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
2689		is typically relocated on 36-bit builds.  It is recommended
2690		that this macro be defined via the _HIGH and _LOW macros:
2691
2692		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
2693			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
2694
2695- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
2696		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
2697		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
2698		used in assembly code, so it must not contain typecasts or
2699		integer size suffixes (e.g. "ULL").
2700
2701- CONFIG_SYS_CCSRBAR_PHYS_LOW:
2702		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
2703		used in assembly code, so it must not contain typecasts or
2704		integer size suffixes (e.g. "ULL").
2705
2706- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
2707		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
2708		forced to a value that ensures that CCSR is not relocated.
2709
2710- CONFIG_IDE_AHB:
2711		Most IDE controllers were designed to be connected with PCI
2712		interface. Only few of them were designed for AHB interface.
2713		When software is doing ATA command and data transfer to
2714		IDE devices through IDE-AHB controller, some additional
2715		registers accessing to these kind of IDE-AHB controller
2716		is required.
2717
2718- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
2719		DO NOT CHANGE unless you know exactly what you're
2720		doing! (11-4) [MPC8xx systems only]
2721
2722- CONFIG_SYS_INIT_RAM_ADDR:
2723
2724		Start address of memory area that can be used for
2725		initial data and stack; please note that this must be
2726		writable memory that is working WITHOUT special
2727		initialization, i. e. you CANNOT use normal RAM which
2728		will become available only after programming the
2729		memory controller and running certain initialization
2730		sequences.
2731
2732		U-Boot uses the following memory types:
2733		- MPC8xx: IMMR (internal memory of the CPU)
2734
2735- CONFIG_SYS_GBL_DATA_OFFSET:
2736
2737		Offset of the initial data structure in the memory
2738		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
2739		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
2740		data is located at the end of the available space
2741		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
2742		GENERATED_GBL_DATA_SIZE), and the initial stack is just
2743		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
2744		CONFIG_SYS_GBL_DATA_OFFSET) downward.
2745
2746	Note:
2747		On the MPC824X (or other systems that use the data
2748		cache for initial memory) the address chosen for
2749		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
2750		point to an otherwise UNUSED address space between
2751		the top of RAM and the start of the PCI space.
2752
2753- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
2754
2755- CONFIG_SYS_OR_TIMING_SDRAM:
2756		SDRAM timing
2757
2758- CONFIG_SYS_MAMR_PTA:
2759		periodic timer for refresh
2760
2761- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
2762  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
2763  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
2764  CONFIG_SYS_BR1_PRELIM:
2765		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
2766
2767- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
2768  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
2769  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
2770		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
2771
2772- CONFIG_PCI_INDIRECT_BRIDGE:
2773		Enable support for indirect PCI bridges.
2774
2775- CONFIG_SYS_SRIO:
2776		Chip has SRIO or not
2777
2778- CONFIG_SRIO1:
2779		Board has SRIO 1 port available
2780
2781- CONFIG_SRIO2:
2782		Board has SRIO 2 port available
2783
2784- CONFIG_SRIO_PCIE_BOOT_MASTER
2785		Board can support master function for Boot from SRIO and PCIE
2786
2787- CONFIG_SYS_SRIOn_MEM_VIRT:
2788		Virtual Address of SRIO port 'n' memory region
2789
2790- CONFIG_SYS_SRIOn_MEM_PHYxS:
2791		Physical Address of SRIO port 'n' memory region
2792
2793- CONFIG_SYS_SRIOn_MEM_SIZE:
2794		Size of SRIO port 'n' memory region
2795
2796- CONFIG_SYS_NAND_BUSWIDTH_16BIT
2797		Defined to tell the NAND controller that the NAND chip is using
2798		a 16 bit bus.
2799		Not all NAND drivers use this symbol.
2800		Example of drivers that use it:
2801		- drivers/mtd/nand/raw/ndfc.c
2802		- drivers/mtd/nand/raw/mxc_nand.c
2803
2804- CONFIG_SYS_NDFC_EBC0_CFG
2805		Sets the EBC0_CFG register for the NDFC. If not defined
2806		a default value will be used.
2807
2808- CONFIG_SPD_EEPROM
2809		Get DDR timing information from an I2C EEPROM. Common
2810		with pluggable memory modules such as SODIMMs
2811
2812  SPD_EEPROM_ADDRESS
2813		I2C address of the SPD EEPROM
2814
2815- CONFIG_SYS_SPD_BUS_NUM
2816		If SPD EEPROM is on an I2C bus other than the first
2817		one, specify here. Note that the value must resolve
2818		to something your driver can deal with.
2819
2820- CONFIG_SYS_DDR_RAW_TIMING
2821		Get DDR timing information from other than SPD. Common with
2822		soldered DDR chips onboard without SPD. DDR raw timing
2823		parameters are extracted from datasheet and hard-coded into
2824		header files or board specific files.
2825
2826- CONFIG_FSL_DDR_INTERACTIVE
2827		Enable interactive DDR debugging. See doc/README.fsl-ddr.
2828
2829- CONFIG_FSL_DDR_SYNC_REFRESH
2830		Enable sync of refresh for multiple controllers.
2831
2832- CONFIG_FSL_DDR_BIST
2833		Enable built-in memory test for Freescale DDR controllers.
2834
2835- CONFIG_SYS_83XX_DDR_USES_CS0
2836		Only for 83xx systems. If specified, then DDR should
2837		be configured using CS0 and CS1 instead of CS2 and CS3.
2838
2839- CONFIG_RMII
2840		Enable RMII mode for all FECs.
2841		Note that this is a global option, we can't
2842		have one FEC in standard MII mode and another in RMII mode.
2843
2844- CONFIG_CRC32_VERIFY
2845		Add a verify option to the crc32 command.
2846		The syntax is:
2847
2848		=> crc32 -v <address> <count> <crc32>
2849
2850		Where address/count indicate a memory area
2851		and crc32 is the correct crc32 which the
2852		area should have.
2853
2854- CONFIG_LOOPW
2855		Add the "loopw" memory command. This only takes effect if
2856		the memory commands are activated globally (CONFIG_CMD_MEMORY).
2857
2858- CONFIG_CMD_MX_CYCLIC
2859		Add the "mdc" and "mwc" memory commands. These are cyclic
2860		"md/mw" commands.
2861		Examples:
2862
2863		=> mdc.b 10 4 500
2864		This command will print 4 bytes (10,11,12,13) each 500 ms.
2865
2866		=> mwc.l 100 12345678 10
2867		This command will write 12345678 to address 100 all 10 ms.
2868
2869		This only takes effect if the memory commands are activated
2870		globally (CONFIG_CMD_MEMORY).
2871
2872- CONFIG_SKIP_LOWLEVEL_INIT
2873		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
2874		low level initializations (like setting up the memory
2875		controller) are omitted and/or U-Boot does not
2876		relocate itself into RAM.
2877
2878		Normally this variable MUST NOT be defined. The only
2879		exception is when U-Boot is loaded (to RAM) by some
2880		other boot loader or by a debugger which performs
2881		these initializations itself.
2882
2883- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
2884		[ARM926EJ-S only] This allows just the call to lowlevel_init()
2885		to be skipped. The normal CP15 init (such as enabling the
2886		instruction cache) is still performed.
2887
2888- CONFIG_SPL_BUILD
2889		Set when the currently-running compilation is for an artifact
2890		that will end up in the SPL (as opposed to the TPL or U-Boot
2891		proper). Code that needs stage-specific behavior should check
2892		this.
2893
2894- CONFIG_TPL_BUILD
2895		Set when the currently-running compilation is for an artifact
2896		that will end up in the TPL (as opposed to the SPL or U-Boot
2897		proper). Code that needs stage-specific behavior should check
2898		this.
2899
2900- CONFIG_SYS_MPC85XX_NO_RESETVEC
2901		Only for 85xx systems. If this variable is specified, the section
2902		.resetvec is not kept and the section .bootpg is placed in the
2903		previous 4k of the .text section.
2904
2905- CONFIG_ARCH_MAP_SYSMEM
2906		Generally U-Boot (and in particular the md command) uses
2907		effective address. It is therefore not necessary to regard
2908		U-Boot address as virtual addresses that need to be translated
2909		to physical addresses. However, sandbox requires this, since
2910		it maintains its own little RAM buffer which contains all
2911		addressable memory. This option causes some memory accesses
2912		to be mapped through map_sysmem() / unmap_sysmem().
2913
2914- CONFIG_X86_RESET_VECTOR
2915		If defined, the x86 reset vector code is included. This is not
2916		needed when U-Boot is running from Coreboot.
2917
2918- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
2919		Option to disable subpage write in NAND driver
2920		driver that uses this:
2921		drivers/mtd/nand/raw/davinci_nand.c
2922
2923Freescale QE/FMAN Firmware Support:
2924-----------------------------------
2925
2926The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
2927loading of "firmware", which is encoded in the QE firmware binary format.
2928This firmware often needs to be loaded during U-Boot booting, so macros
2929are used to identify the storage device (NOR flash, SPI, etc) and the address
2930within that device.
2931
2932- CONFIG_SYS_FMAN_FW_ADDR
2933	The address in the storage device where the FMAN microcode is located.  The
2934	meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2935	is also specified.
2936
2937- CONFIG_SYS_QE_FW_ADDR
2938	The address in the storage device where the QE microcode is located.  The
2939	meaning of this address depends on which CONFIG_SYS_QE_FMAN_FW_IN_xxx macro
2940	is also specified.
2941
2942- CONFIG_SYS_QE_FMAN_FW_LENGTH
2943	The maximum possible size of the firmware.  The firmware binary format
2944	has a field that specifies the actual size of the firmware, but it
2945	might not be possible to read any part of the firmware unless some
2946	local storage is allocated to hold the entire firmware first.
2947
2948- CONFIG_SYS_QE_FMAN_FW_IN_NOR
2949	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
2950	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
2951	virtual address in NOR flash.
2952
2953- CONFIG_SYS_QE_FMAN_FW_IN_NAND
2954	Specifies that QE/FMAN firmware is located in NAND flash.
2955	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
2956
2957- CONFIG_SYS_QE_FMAN_FW_IN_MMC
2958	Specifies that QE/FMAN firmware is located on the primary SD/MMC
2959	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
2960
2961- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
2962	Specifies that QE/FMAN firmware is located in the remote (master)
2963	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
2964	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
2965	window->master inbound window->master LAW->the ucode address in
2966	master's memory space.
2967
2968Freescale Layerscape Management Complex Firmware Support:
2969---------------------------------------------------------
2970The Freescale Layerscape Management Complex (MC) supports the loading of
2971"firmware".
2972This firmware often needs to be loaded during U-Boot booting, so macros
2973are used to identify the storage device (NOR flash, SPI, etc) and the address
2974within that device.
2975
2976- CONFIG_FSL_MC_ENET
2977	Enable the MC driver for Layerscape SoCs.
2978
2979Freescale Layerscape Debug Server Support:
2980-------------------------------------------
2981The Freescale Layerscape Debug Server Support supports the loading of
2982"Debug Server firmware" and triggering SP boot-rom.
2983This firmware often needs to be loaded during U-Boot booting.
2984
2985- CONFIG_SYS_MC_RSV_MEM_ALIGN
2986	Define alignment of reserved memory MC requires
2987
2988Reproducible builds
2989-------------------
2990
2991In order to achieve reproducible builds, timestamps used in the U-Boot build
2992process have to be set to a fixed value.
2993
2994This is done using the SOURCE_DATE_EPOCH environment variable.
2995SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
2996option for U-Boot or an environment variable in U-Boot.
2997
2998SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
2999
3000Building the Software:
3001======================
3002
3003Building U-Boot has been tested in several native build environments
3004and in many different cross environments. Of course we cannot support
3005all possibly existing versions of cross development tools in all
3006(potentially obsolete) versions. In case of tool chain problems we
3007recommend to use the ELDK (see https://www.denx.de/wiki/DULG/ELDK)
3008which is extensively used to build and test U-Boot.
3009
3010If you are not using a native environment, it is assumed that you
3011have GNU cross compiling tools available in your path. In this case,
3012you must set the environment variable CROSS_COMPILE in your shell.
3013Note that no changes to the Makefile or any other source files are
3014necessary. For example using the ELDK on a 4xx CPU, please enter:
3015
3016	$ CROSS_COMPILE=ppc_4xx-
3017	$ export CROSS_COMPILE
3018
3019U-Boot is intended to be simple to build. After installing the
3020sources you must configure U-Boot for one specific board type. This
3021is done by typing:
3022
3023	make NAME_defconfig
3024
3025where "NAME_defconfig" is the name of one of the existing configu-
3026rations; see configs/*_defconfig for supported names.
3027
3028Note: for some boards special configuration names may exist; check if
3029      additional information is available from the board vendor; for
3030      instance, the TQM823L systems are available without (standard)
3031      or with LCD support. You can select such additional "features"
3032      when choosing the configuration, i. e.
3033
3034      make TQM823L_defconfig
3035	- will configure for a plain TQM823L, i. e. no LCD support
3036
3037      make TQM823L_LCD_defconfig
3038	- will configure for a TQM823L with U-Boot console on LCD
3039
3040      etc.
3041
3042
3043Finally, type "make all", and you should get some working U-Boot
3044images ready for download to / installation on your system:
3045
3046- "u-boot.bin" is a raw binary image
3047- "u-boot" is an image in ELF binary format
3048- "u-boot.srec" is in Motorola S-Record format
3049
3050By default the build is performed locally and the objects are saved
3051in the source directory. One of the two methods can be used to change
3052this behavior and build U-Boot to some external directory:
3053
30541. Add O= to the make command line invocations:
3055
3056	make O=/tmp/build distclean
3057	make O=/tmp/build NAME_defconfig
3058	make O=/tmp/build all
3059
30602. Set environment variable KBUILD_OUTPUT to point to the desired location:
3061
3062	export KBUILD_OUTPUT=/tmp/build
3063	make distclean
3064	make NAME_defconfig
3065	make all
3066
3067Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3068variable.
3069
3070User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3071setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3072For example to treat all compiler warnings as errors:
3073
3074	make KCFLAGS=-Werror
3075
3076Please be aware that the Makefiles assume you are using GNU make, so
3077for instance on NetBSD you might need to use "gmake" instead of
3078native "make".
3079
3080
3081If the system board that you have is not listed, then you will need
3082to port U-Boot to your hardware platform. To do this, follow these
3083steps:
3084
30851.  Create a new directory to hold your board specific code. Add any
3086    files you need. In your board directory, you will need at least
3087    the "Makefile" and a "<board>.c".
30882.  Create a new configuration file "include/configs/<board>.h" for
3089    your board.
30903.  If you're porting U-Boot to a new CPU, then also create a new
3091    directory to hold your CPU specific code. Add any files you need.
30924.  Run "make <board>_defconfig" with your new name.
30935.  Type "make", and you should get a working "u-boot.srec" file
3094    to be installed on your target system.
30956.  Debug and solve any problems that might arise.
3096    [Of course, this last step is much harder than it sounds.]
3097
3098
3099Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3100==============================================================
3101
3102If you have modified U-Boot sources (for instance added a new board
3103or support for new devices, a new CPU, etc.) you are expected to
3104provide feedback to the other developers. The feedback normally takes
3105the form of a "patch", i.e. a context diff against a certain (latest
3106official or latest in the git repository) version of U-Boot sources.
3107
3108But before you submit such a patch, please verify that your modifi-
3109cation did not break existing code. At least make sure that *ALL* of
3110the supported boards compile WITHOUT ANY compiler warnings. To do so,
3111just run the buildman script (tools/buildman/buildman), which will
3112configure and build U-Boot for ALL supported system. Be warned, this
3113will take a while. Please see the buildman README, or run 'buildman -H'
3114for documentation.
3115
3116
3117See also "U-Boot Porting Guide" below.
3118
3119
3120Monitor Commands - Overview:
3121============================
3122
3123go	- start application at address 'addr'
3124run	- run commands in an environment variable
3125bootm	- boot application image from memory
3126bootp	- boot image via network using BootP/TFTP protocol
3127bootz   - boot zImage from memory
3128tftpboot- boot image via network using TFTP protocol
3129	       and env variables "ipaddr" and "serverip"
3130	       (and eventually "gatewayip")
3131tftpput - upload a file via network using TFTP protocol
3132rarpboot- boot image via network using RARP/TFTP protocol
3133diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3134loads	- load S-Record file over serial line
3135loadb	- load binary file over serial line (kermit mode)
3136md	- memory display
3137mm	- memory modify (auto-incrementing)
3138nm	- memory modify (constant address)
3139mw	- memory write (fill)
3140ms	- memory search
3141cp	- memory copy
3142cmp	- memory compare
3143crc32	- checksum calculation
3144i2c	- I2C sub-system
3145sspi	- SPI utility commands
3146base	- print or set address offset
3147printenv- print environment variables
3148pwm	- control pwm channels
3149setenv	- set environment variables
3150saveenv - save environment variables to persistent storage
3151protect - enable or disable FLASH write protection
3152erase	- erase FLASH memory
3153flinfo	- print FLASH memory information
3154nand	- NAND memory operations (see doc/README.nand)
3155bdinfo	- print Board Info structure
3156iminfo	- print header information for application image
3157coninfo - print console devices and informations
3158ide	- IDE sub-system
3159loop	- infinite loop on address range
3160loopw	- infinite write loop on address range
3161mtest	- simple RAM test
3162icache	- enable or disable instruction cache
3163dcache	- enable or disable data cache
3164reset	- Perform RESET of the CPU
3165echo	- echo args to console
3166version - print monitor version
3167help	- print online help
3168?	- alias for 'help'
3169
3170
3171Monitor Commands - Detailed Description:
3172========================================
3173
3174TODO.
3175
3176For now: just type "help <command>".
3177
3178
3179Environment Variables:
3180======================
3181
3182U-Boot supports user configuration using Environment Variables which
3183can be made persistent by saving to Flash memory.
3184
3185Environment Variables are set using "setenv", printed using
3186"printenv", and saved to Flash using "saveenv". Using "setenv"
3187without a value can be used to delete a variable from the
3188environment. As long as you don't save the environment you are
3189working with an in-memory copy. In case the Flash area containing the
3190environment is erased by accident, a default environment is provided.
3191
3192Some configuration options can be set using Environment Variables.
3193
3194List of environment variables (most likely not complete):
3195
3196  baudrate	- see CONFIG_BAUDRATE
3197
3198  bootdelay	- see CONFIG_BOOTDELAY
3199
3200  bootcmd	- see CONFIG_BOOTCOMMAND
3201
3202  bootargs	- Boot arguments when booting an RTOS image
3203
3204  bootfile	- Name of the image to load with TFTP
3205
3206  bootm_low	- Memory range available for image processing in the bootm
3207		  command can be restricted. This variable is given as
3208		  a hexadecimal number and defines lowest address allowed
3209		  for use by the bootm command. See also "bootm_size"
3210		  environment variable. Address defined by "bootm_low" is
3211		  also the base of the initial memory mapping for the Linux
3212		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3213		  bootm_mapsize.
3214
3215  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3216		  This variable is given as a hexadecimal number and it
3217		  defines the size of the memory region starting at base
3218		  address bootm_low that is accessible by the Linux kernel
3219		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3220		  as the default value if it is defined, and bootm_size is
3221		  used otherwise.
3222
3223  bootm_size	- Memory range available for image processing in the bootm
3224		  command can be restricted. This variable is given as
3225		  a hexadecimal number and defines the size of the region
3226		  allowed for use by the bootm command. See also "bootm_low"
3227		  environment variable.
3228
3229  bootstopkeysha256, bootdelaykey, bootstopkey	- See README.autoboot
3230
3231  updatefile	- Location of the software update file on a TFTP server, used
3232		  by the automatic software update feature. Please refer to
3233		  documentation in doc/README.update for more details.
3234
3235  autoload	- if set to "no" (any string beginning with 'n'),
3236		  "bootp" will just load perform a lookup of the
3237		  configuration from the BOOTP server, but not try to
3238		  load any image using TFTP
3239
3240  autostart	- if set to "yes", an image loaded using the "bootp",
3241		  "rarpboot", "tftpboot" or "diskboot" commands will
3242		  be automatically started (by internally calling
3243		  "bootm")
3244
3245		  If set to "no", a standalone image passed to the
3246		  "bootm" command will be copied to the load address
3247		  (and eventually uncompressed), but NOT be started.
3248		  This can be used to load and uncompress arbitrary
3249		  data.
3250
3251  fdt_high	- if set this restricts the maximum address that the
3252		  flattened device tree will be copied into upon boot.
3253		  For example, if you have a system with 1 GB memory
3254		  at physical address 0x10000000, while Linux kernel
3255		  only recognizes the first 704 MB as low memory, you
3256		  may need to set fdt_high as 0x3C000000 to have the
3257		  device tree blob be copied to the maximum address
3258		  of the 704 MB low memory, so that Linux kernel can
3259		  access it during the boot procedure.
3260
3261		  If this is set to the special value 0xFFFFFFFF then
3262		  the fdt will not be copied at all on boot.  For this
3263		  to work it must reside in writable memory, have
3264		  sufficient padding on the end of it for u-boot to
3265		  add the information it needs into it, and the memory
3266		  must be accessible by the kernel.
3267
3268  fdtcontroladdr- if set this is the address of the control flattened
3269		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3270		  defined.
3271
3272  i2cfast	- (PPC405GP|PPC405EP only)
3273		  if set to 'y' configures Linux I2C driver for fast
3274		  mode (400kHZ). This environment variable is used in
3275		  initialization code. So, for changes to be effective
3276		  it must be saved and board must be reset.
3277
3278  initrd_high	- restrict positioning of initrd images:
3279		  If this variable is not set, initrd images will be
3280		  copied to the highest possible address in RAM; this
3281		  is usually what you want since it allows for
3282		  maximum initrd size. If for some reason you want to
3283		  make sure that the initrd image is loaded below the
3284		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3285		  variable to a value of "no" or "off" or "0".
3286		  Alternatively, you can set it to a maximum upper
3287		  address to use (U-Boot will still check that it
3288		  does not overwrite the U-Boot stack and data).
3289
3290		  For instance, when you have a system with 16 MB
3291		  RAM, and want to reserve 4 MB from use by Linux,
3292		  you can do this by adding "mem=12M" to the value of
3293		  the "bootargs" variable. However, now you must make
3294		  sure that the initrd image is placed in the first
3295		  12 MB as well - this can be done with
3296
3297		  setenv initrd_high 00c00000
3298
3299		  If you set initrd_high to 0xFFFFFFFF, this is an
3300		  indication to U-Boot that all addresses are legal
3301		  for the Linux kernel, including addresses in flash
3302		  memory. In this case U-Boot will NOT COPY the
3303		  ramdisk at all. This may be useful to reduce the
3304		  boot time on your system, but requires that this
3305		  feature is supported by your Linux kernel.
3306
3307  ipaddr	- IP address; needed for tftpboot command
3308
3309  loadaddr	- Default load address for commands like "bootp",
3310		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3311
3312  loads_echo	- see CONFIG_LOADS_ECHO
3313
3314  serverip	- TFTP server IP address; needed for tftpboot command
3315
3316  bootretry	- see CONFIG_BOOT_RETRY_TIME
3317
3318  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3319
3320  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3321
3322  ethprime	- controls which interface is used first.
3323
3324  ethact	- controls which interface is currently active.
3325		  For example you can do the following
3326
3327		  => setenv ethact FEC
3328		  => ping 192.168.0.1 # traffic sent on FEC
3329		  => setenv ethact SCC
3330		  => ping 10.0.0.1 # traffic sent on SCC
3331
3332  ethrotate	- When set to "no" U-Boot does not go through all
3333		  available network interfaces.
3334		  It just stays at the currently selected interface.
3335
3336  netretry	- When set to "no" each network operation will
3337		  either succeed or fail without retrying.
3338		  When set to "once" the network operation will
3339		  fail when all the available network interfaces
3340		  are tried once without success.
3341		  Useful on scripts which control the retry operation
3342		  themselves.
3343
3344  npe_ucode	- set load address for the NPE microcode
3345
3346  silent_linux  - If set then Linux will be told to boot silently, by
3347		  changing the console to be empty. If "yes" it will be
3348		  made silent. If "no" it will not be made silent. If
3349		  unset, then it will be made silent if the U-Boot console
3350		  is silent.
3351
3352  tftpsrcp	- If this is set, the value is used for TFTP's
3353		  UDP source port.
3354
3355  tftpdstp	- If this is set, the value is used for TFTP's UDP
3356		  destination port instead of the Well Know Port 69.
3357
3358  tftpblocksize - Block size to use for TFTP transfers; if not set,
3359		  we use the TFTP server's default block size
3360
3361  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3362		  seconds, minimum value is 1000 = 1 second). Defines
3363		  when a packet is considered to be lost so it has to
3364		  be retransmitted. The default is 5000 = 5 seconds.
3365		  Lowering this value may make downloads succeed
3366		  faster in networks with high packet loss rates or
3367		  with unreliable TFTP servers.
3368
3369  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3370		  unit, minimum value = 0). Defines how many timeouts
3371		  can happen during a single file transfer before that
3372		  transfer is aborted. The default is 10, and 0 means
3373		  'no timeouts allowed'. Increasing this value may help
3374		  downloads succeed with high packet loss rates, or with
3375		  unreliable TFTP servers or client hardware.
3376
3377  tftpwindowsize	- if this is set, the value is used for TFTP's
3378		  window size as described by RFC 7440.
3379		  This means the count of blocks we can receive before
3380		  sending ack to server.
3381
3382  vlan		- When set to a value < 4095 the traffic over
3383		  Ethernet is encapsulated/received over 802.1q
3384		  VLAN tagged frames.
3385
3386  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3387		  Unsigned value, in milliseconds. If not set, the period will
3388		  be either the default (28000), or a value based on
3389		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3390		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3391
3392  memmatches	- Number of matches found by the last 'ms' command, in hex
3393
3394  memaddr	- Address of the last match found by the 'ms' command, in hex,
3395		  or 0 if none
3396
3397  mempos	- Index position of the last match found by the 'ms' command,
3398		  in units of the size (.b, .w, .l) of the search
3399
3400  zbootbase	- (x86 only) Base address of the bzImage 'setup' block
3401
3402  zbootaddr	- (x86 only) Address of the loaded bzImage, typically
3403		  BZIMAGE_LOAD_ADDR which is 0x100000
3404
3405The following image location variables contain the location of images
3406used in booting. The "Image" column gives the role of the image and is
3407not an environment variable name. The other columns are environment
3408variable names. "File Name" gives the name of the file on a TFTP
3409server, "RAM Address" gives the location in RAM the image will be
3410loaded to, and "Flash Location" gives the image's address in NOR
3411flash or offset in NAND flash.
3412
3413*Note* - these variables don't have to be defined for all boards, some
3414boards currently use other variables for these purposes, and some
3415boards use these variables for other purposes.
3416
3417Image		    File Name	     RAM Address       Flash Location
3418-----		    ---------	     -----------       --------------
3419u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3420Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3421device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3422ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3423
3424The following environment variables may be used and automatically
3425updated by the network boot commands ("bootp" and "rarpboot"),
3426depending the information provided by your boot server:
3427
3428  bootfile	- see above
3429  dnsip		- IP address of your Domain Name Server
3430  dnsip2	- IP address of your secondary Domain Name Server
3431  gatewayip	- IP address of the Gateway (Router) to use
3432  hostname	- Target hostname
3433  ipaddr	- see above
3434  netmask	- Subnet Mask
3435  rootpath	- Pathname of the root filesystem on the NFS server
3436  serverip	- see above
3437
3438
3439There are two special Environment Variables:
3440
3441  serial#	- contains hardware identification information such
3442		  as type string and/or serial number
3443  ethaddr	- Ethernet address
3444
3445These variables can be set only once (usually during manufacturing of
3446the board). U-Boot refuses to delete or overwrite these variables
3447once they have been set once.
3448
3449
3450Further special Environment Variables:
3451
3452  ver		- Contains the U-Boot version string as printed
3453		  with the "version" command. This variable is
3454		  readonly (see CONFIG_VERSION_VARIABLE).
3455
3456
3457Please note that changes to some configuration parameters may take
3458only effect after the next boot (yes, that's just like Windoze :-).
3459
3460
3461Callback functions for environment variables:
3462---------------------------------------------
3463
3464For some environment variables, the behavior of u-boot needs to change
3465when their values are changed.  This functionality allows functions to
3466be associated with arbitrary variables.  On creation, overwrite, or
3467deletion, the callback will provide the opportunity for some side
3468effect to happen or for the change to be rejected.
3469
3470The callbacks are named and associated with a function using the
3471U_BOOT_ENV_CALLBACK macro in your board or driver code.
3472
3473These callbacks are associated with variables in one of two ways.  The
3474static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3475in the board configuration to a string that defines a list of
3476associations.  The list must be in the following format:
3477
3478	entry = variable_name[:callback_name]
3479	list = entry[,list]
3480
3481If the callback name is not specified, then the callback is deleted.
3482Spaces are also allowed anywhere in the list.
3483
3484Callbacks can also be associated by defining the ".callbacks" variable
3485with the same list format above.  Any association in ".callbacks" will
3486override any association in the static list. You can define
3487CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3488".callbacks" environment variable in the default or embedded environment.
3489
3490If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3491regular expression. This allows multiple variables to be connected to
3492the same callback without explicitly listing them all out.
3493
3494The signature of the callback functions is:
3495
3496    int callback(const char *name, const char *value, enum env_op op, int flags)
3497
3498* name - changed environment variable
3499* value - new value of the environment variable
3500* op - operation (create, overwrite, or delete)
3501* flags - attributes of the environment variable change, see flags H_* in
3502  include/search.h
3503
3504The return value is 0 if the variable change is accepted and 1 otherwise.
3505
3506Command Line Parsing:
3507=====================
3508
3509There are two different command line parsers available with U-Boot:
3510the old "simple" one, and the much more powerful "hush" shell:
3511
3512Old, simple command line parser:
3513--------------------------------
3514
3515- supports environment variables (through setenv / saveenv commands)
3516- several commands on one line, separated by ';'
3517- variable substitution using "... ${name} ..." syntax
3518- special characters ('$', ';') can be escaped by prefixing with '\',
3519  for example:
3520	setenv bootcmd bootm \${address}
3521- You can also escape text by enclosing in single apostrophes, for example:
3522	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3523
3524Hush shell:
3525-----------
3526
3527- similar to Bourne shell, with control structures like
3528  if...then...else...fi, for...do...done; while...do...done,
3529  until...do...done, ...
3530- supports environment ("global") variables (through setenv / saveenv
3531  commands) and local shell variables (through standard shell syntax
3532  "name=value"); only environment variables can be used with "run"
3533  command
3534
3535General rules:
3536--------------
3537
3538(1) If a command line (or an environment variable executed by a "run"
3539    command) contains several commands separated by semicolon, and
3540    one of these commands fails, then the remaining commands will be
3541    executed anyway.
3542
3543(2) If you execute several variables with one call to run (i. e.
3544    calling run with a list of variables as arguments), any failing
3545    command will cause "run" to terminate, i. e. the remaining
3546    variables are not executed.
3547
3548Note for Redundant Ethernet Interfaces:
3549=======================================
3550
3551Some boards come with redundant Ethernet interfaces; U-Boot supports
3552such configurations and is capable of automatic selection of a
3553"working" interface when needed. MAC assignment works as follows:
3554
3555Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3556MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3557"eth1addr" (=>eth1), "eth2addr", ...
3558
3559If the network interface stores some valid MAC address (for instance
3560in SROM), this is used as default address if there is NO correspon-
3561ding setting in the environment; if the corresponding environment
3562variable is set, this overrides the settings in the card; that means:
3563
3564o If the SROM has a valid MAC address, and there is no address in the
3565  environment, the SROM's address is used.
3566
3567o If there is no valid address in the SROM, and a definition in the
3568  environment exists, then the value from the environment variable is
3569  used.
3570
3571o If both the SROM and the environment contain a MAC address, and
3572  both addresses are the same, this MAC address is used.
3573
3574o If both the SROM and the environment contain a MAC address, and the
3575  addresses differ, the value from the environment is used and a
3576  warning is printed.
3577
3578o If neither SROM nor the environment contain a MAC address, an error
3579  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
3580  a random, locally-assigned MAC is used.
3581
3582If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
3583will be programmed into hardware as part of the initialization process.	 This
3584may be skipped by setting the appropriate 'ethmacskip' environment variable.
3585The naming convention is as follows:
3586"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
3587
3588Image Formats:
3589==============
3590
3591U-Boot is capable of booting (and performing other auxiliary operations on)
3592images in two formats:
3593
3594New uImage format (FIT)
3595-----------------------
3596
3597Flexible and powerful format based on Flattened Image Tree -- FIT (similar
3598to Flattened Device Tree). It allows the use of images with multiple
3599components (several kernels, ramdisks, etc.), with contents protected by
3600SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
3601
3602
3603Old uImage format
3604-----------------
3605
3606Old image format is based on binary files which can be basically anything,
3607preceded by a special header; see the definitions in include/image.h for
3608details; basically, the header defines the following image properties:
3609
3610* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
3611  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
3612  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
3613  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
3614  INTEGRITY).
3615* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
3616  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
3617  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
3618* Compression Type (uncompressed, gzip, bzip2)
3619* Load Address
3620* Entry Point
3621* Image Name
3622* Image Timestamp
3623
3624The header is marked by a special Magic Number, and both the header
3625and the data portions of the image are secured against corruption by
3626CRC32 checksums.
3627
3628
3629Linux Support:
3630==============
3631
3632Although U-Boot should support any OS or standalone application
3633easily, the main focus has always been on Linux during the design of
3634U-Boot.
3635
3636U-Boot includes many features that so far have been part of some
3637special "boot loader" code within the Linux kernel. Also, any
3638"initrd" images to be used are no longer part of one big Linux image;
3639instead, kernel and "initrd" are separate images. This implementation
3640serves several purposes:
3641
3642- the same features can be used for other OS or standalone
3643  applications (for instance: using compressed images to reduce the
3644  Flash memory footprint)
3645
3646- it becomes much easier to port new Linux kernel versions because
3647  lots of low-level, hardware dependent stuff are done by U-Boot
3648
3649- the same Linux kernel image can now be used with different "initrd"
3650  images; of course this also means that different kernel images can
3651  be run with the same "initrd". This makes testing easier (you don't
3652  have to build a new "zImage.initrd" Linux image when you just
3653  change a file in your "initrd"). Also, a field-upgrade of the
3654  software is easier now.
3655
3656
3657Linux HOWTO:
3658============
3659
3660Porting Linux to U-Boot based systems:
3661---------------------------------------
3662
3663U-Boot cannot save you from doing all the necessary modifications to
3664configure the Linux device drivers for use with your target hardware
3665(no, we don't intend to provide a full virtual machine interface to
3666Linux :-).
3667
3668But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
3669
3670Just make sure your machine specific header file (for instance
3671include/asm-ppc/tqm8xx.h) includes the same definition of the Board
3672Information structure as we define in include/asm-<arch>/u-boot.h,
3673and make sure that your definition of IMAP_ADDR uses the same value
3674as your U-Boot configuration in CONFIG_SYS_IMMR.
3675
3676Note that U-Boot now has a driver model, a unified model for drivers.
3677If you are adding a new driver, plumb it into driver model. If there
3678is no uclass available, you are encouraged to create one. See
3679doc/driver-model.
3680
3681
3682Configuring the Linux kernel:
3683-----------------------------
3684
3685No specific requirements for U-Boot. Make sure you have some root
3686device (initial ramdisk, NFS) for your target system.
3687
3688
3689Building a Linux Image:
3690-----------------------
3691
3692With U-Boot, "normal" build targets like "zImage" or "bzImage" are
3693not used. If you use recent kernel source, a new build target
3694"uImage" will exist which automatically builds an image usable by
3695U-Boot. Most older kernels also have support for a "pImage" target,
3696which was introduced for our predecessor project PPCBoot and uses a
3697100% compatible format.
3698
3699Example:
3700
3701	make TQM850L_defconfig
3702	make oldconfig
3703	make dep
3704	make uImage
3705
3706The "uImage" build target uses a special tool (in 'tools/mkimage') to
3707encapsulate a compressed Linux kernel image with header	 information,
3708CRC32 checksum etc. for use with U-Boot. This is what we are doing:
3709
3710* build a standard "vmlinux" kernel image (in ELF binary format):
3711
3712* convert the kernel into a raw binary image:
3713
3714	${CROSS_COMPILE}-objcopy -O binary \
3715				 -R .note -R .comment \
3716				 -S vmlinux linux.bin
3717
3718* compress the binary image:
3719
3720	gzip -9 linux.bin
3721
3722* package compressed binary image for U-Boot:
3723
3724	mkimage -A ppc -O linux -T kernel -C gzip \
3725		-a 0 -e 0 -n "Linux Kernel Image" \
3726		-d linux.bin.gz uImage
3727
3728
3729The "mkimage" tool can also be used to create ramdisk images for use
3730with U-Boot, either separated from the Linux kernel image, or
3731combined into one file. "mkimage" encapsulates the images with a 64
3732byte header containing information about target architecture,
3733operating system, image type, compression method, entry points, time
3734stamp, CRC32 checksums, etc.
3735
3736"mkimage" can be called in two ways: to verify existing images and
3737print the header information, or to build new images.
3738
3739In the first form (with "-l" option) mkimage lists the information
3740contained in the header of an existing U-Boot image; this includes
3741checksum verification:
3742
3743	tools/mkimage -l image
3744	  -l ==> list image header information
3745
3746The second form (with "-d" option) is used to build a U-Boot image
3747from a "data file" which is used as image payload:
3748
3749	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
3750		      -n name -d data_file image
3751	  -A ==> set architecture to 'arch'
3752	  -O ==> set operating system to 'os'
3753	  -T ==> set image type to 'type'
3754	  -C ==> set compression type 'comp'
3755	  -a ==> set load address to 'addr' (hex)
3756	  -e ==> set entry point to 'ep' (hex)
3757	  -n ==> set image name to 'name'
3758	  -d ==> use image data from 'datafile'
3759
3760Right now, all Linux kernels for PowerPC systems use the same load
3761address (0x00000000), but the entry point address depends on the
3762kernel version:
3763
3764- 2.2.x kernels have the entry point at 0x0000000C,
3765- 2.3.x and later kernels have the entry point at 0x00000000.
3766
3767So a typical call to build a U-Boot image would read:
3768
3769	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3770	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
3771	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
3772	> examples/uImage.TQM850L
3773	Image Name:   2.4.4 kernel for TQM850L
3774	Created:      Wed Jul 19 02:34:59 2000
3775	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3776	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3777	Load Address: 0x00000000
3778	Entry Point:  0x00000000
3779
3780To verify the contents of the image (or check for corruption):
3781
3782	-> tools/mkimage -l examples/uImage.TQM850L
3783	Image Name:   2.4.4 kernel for TQM850L
3784	Created:      Wed Jul 19 02:34:59 2000
3785	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
3786	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
3787	Load Address: 0x00000000
3788	Entry Point:  0x00000000
3789
3790NOTE: for embedded systems where boot time is critical you can trade
3791speed for memory and install an UNCOMPRESSED image instead: this
3792needs more space in Flash, but boots much faster since it does not
3793need to be uncompressed:
3794
3795	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
3796	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
3797	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
3798	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
3799	> examples/uImage.TQM850L-uncompressed
3800	Image Name:   2.4.4 kernel for TQM850L
3801	Created:      Wed Jul 19 02:34:59 2000
3802	Image Type:   PowerPC Linux Kernel Image (uncompressed)
3803	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
3804	Load Address: 0x00000000
3805	Entry Point:  0x00000000
3806
3807
3808Similar you can build U-Boot images from a 'ramdisk.image.gz' file
3809when your kernel is intended to use an initial ramdisk:
3810
3811	-> tools/mkimage -n 'Simple Ramdisk Image' \
3812	> -A ppc -O linux -T ramdisk -C gzip \
3813	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
3814	Image Name:   Simple Ramdisk Image
3815	Created:      Wed Jan 12 14:01:50 2000
3816	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
3817	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
3818	Load Address: 0x00000000
3819	Entry Point:  0x00000000
3820
3821The "dumpimage" tool can be used to disassemble or list the contents of images
3822built by mkimage. See dumpimage's help output (-h) for details.
3823
3824Installing a Linux Image:
3825-------------------------
3826
3827To downloading a U-Boot image over the serial (console) interface,
3828you must convert the image to S-Record format:
3829
3830	objcopy -I binary -O srec examples/image examples/image.srec
3831
3832The 'objcopy' does not understand the information in the U-Boot
3833image header, so the resulting S-Record file will be relative to
3834address 0x00000000. To load it to a given address, you need to
3835specify the target address as 'offset' parameter with the 'loads'
3836command.
3837
3838Example: install the image to address 0x40100000 (which on the
3839TQM8xxL is in the first Flash bank):
3840
3841	=> erase 40100000 401FFFFF
3842
3843	.......... done
3844	Erased 8 sectors
3845
3846	=> loads 40100000
3847	## Ready for S-Record download ...
3848	~>examples/image.srec
3849	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
3850	...
3851	15989 15990 15991 15992
3852	[file transfer complete]
3853	[connected]
3854	## Start Addr = 0x00000000
3855
3856
3857You can check the success of the download using the 'iminfo' command;
3858this includes a checksum verification so you can be sure no data
3859corruption happened:
3860
3861	=> imi 40100000
3862
3863	## Checking Image at 40100000 ...
3864	   Image Name:	 2.2.13 for initrd on TQM850L
3865	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3866	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3867	   Load Address: 00000000
3868	   Entry Point:	 0000000c
3869	   Verifying Checksum ... OK
3870
3871
3872Boot Linux:
3873-----------
3874
3875The "bootm" command is used to boot an application that is stored in
3876memory (RAM or Flash). In case of a Linux kernel image, the contents
3877of the "bootargs" environment variable is passed to the kernel as
3878parameters. You can check and modify this variable using the
3879"printenv" and "setenv" commands:
3880
3881
3882	=> printenv bootargs
3883	bootargs=root=/dev/ram
3884
3885	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3886
3887	=> printenv bootargs
3888	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3889
3890	=> bootm 40020000
3891	## Booting Linux kernel at 40020000 ...
3892	   Image Name:	 2.2.13 for NFS on TQM850L
3893	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3894	   Data Size:	 381681 Bytes = 372 kB = 0 MB
3895	   Load Address: 00000000
3896	   Entry Point:	 0000000c
3897	   Verifying Checksum ... OK
3898	   Uncompressing Kernel Image ... OK
3899	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
3900	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
3901	time_init: decrementer frequency = 187500000/60
3902	Calibrating delay loop... 49.77 BogoMIPS
3903	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
3904	...
3905
3906If you want to boot a Linux kernel with initial RAM disk, you pass
3907the memory addresses of both the kernel and the initrd image (PPBCOOT
3908format!) to the "bootm" command:
3909
3910	=> imi 40100000 40200000
3911
3912	## Checking Image at 40100000 ...
3913	   Image Name:	 2.2.13 for initrd on TQM850L
3914	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3915	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3916	   Load Address: 00000000
3917	   Entry Point:	 0000000c
3918	   Verifying Checksum ... OK
3919
3920	## Checking Image at 40200000 ...
3921	   Image Name:	 Simple Ramdisk Image
3922	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
3923	   Data Size:	 566530 Bytes = 553 kB = 0 MB
3924	   Load Address: 00000000
3925	   Entry Point:	 00000000
3926	   Verifying Checksum ... OK
3927
3928	=> bootm 40100000 40200000
3929	## Booting Linux kernel at 40100000 ...
3930	   Image Name:	 2.2.13 for initrd on TQM850L
3931	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3932	   Data Size:	 335725 Bytes = 327 kB = 0 MB
3933	   Load Address: 00000000
3934	   Entry Point:	 0000000c
3935	   Verifying Checksum ... OK
3936	   Uncompressing Kernel Image ... OK
3937	## Loading RAMDisk Image at 40200000 ...
3938	   Image Name:	 Simple Ramdisk Image
3939	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
3940	   Data Size:	 566530 Bytes = 553 kB = 0 MB
3941	   Load Address: 00000000
3942	   Entry Point:	 00000000
3943	   Verifying Checksum ... OK
3944	   Loading Ramdisk ... OK
3945	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
3946	Boot arguments: root=/dev/ram
3947	time_init: decrementer frequency = 187500000/60
3948	Calibrating delay loop... 49.77 BogoMIPS
3949	...
3950	RAMDISK: Compressed image found at block 0
3951	VFS: Mounted root (ext2 filesystem).
3952
3953	bash#
3954
3955Boot Linux and pass a flat device tree:
3956-----------
3957
3958First, U-Boot must be compiled with the appropriate defines. See the section
3959titled "Linux Kernel Interface" above for a more in depth explanation. The
3960following is an example of how to start a kernel and pass an updated
3961flat device tree:
3962
3963=> print oftaddr
3964oftaddr=0x300000
3965=> print oft
3966oft=oftrees/mpc8540ads.dtb
3967=> tftp $oftaddr $oft
3968Speed: 1000, full duplex
3969Using TSEC0 device
3970TFTP from server 192.168.1.1; our IP address is 192.168.1.101
3971Filename 'oftrees/mpc8540ads.dtb'.
3972Load address: 0x300000
3973Loading: #
3974done
3975Bytes transferred = 4106 (100a hex)
3976=> tftp $loadaddr $bootfile
3977Speed: 1000, full duplex
3978Using TSEC0 device
3979TFTP from server 192.168.1.1; our IP address is 192.168.1.2
3980Filename 'uImage'.
3981Load address: 0x200000
3982Loading:############
3983done
3984Bytes transferred = 1029407 (fb51f hex)
3985=> print loadaddr
3986loadaddr=200000
3987=> print oftaddr
3988oftaddr=0x300000
3989=> bootm $loadaddr - $oftaddr
3990## Booting image at 00200000 ...
3991   Image Name:	 Linux-2.6.17-dirty
3992   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
3993   Data Size:	 1029343 Bytes = 1005.2 kB
3994   Load Address: 00000000
3995   Entry Point:	 00000000
3996   Verifying Checksum ... OK
3997   Uncompressing Kernel Image ... OK
3998Booting using flat device tree at 0x300000
3999Using MPC85xx ADS machine description
4000Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4001[snip]
4002
4003
4004More About U-Boot Image Types:
4005------------------------------
4006
4007U-Boot supports the following image types:
4008
4009   "Standalone Programs" are directly runnable in the environment
4010	provided by U-Boot; it is expected that (if they behave
4011	well) you can continue to work in U-Boot after return from
4012	the Standalone Program.
4013   "OS Kernel Images" are usually images of some Embedded OS which
4014	will take over control completely. Usually these programs
4015	will install their own set of exception handlers, device
4016	drivers, set up the MMU, etc. - this means, that you cannot
4017	expect to re-enter U-Boot except by resetting the CPU.
4018   "RAMDisk Images" are more or less just data blocks, and their
4019	parameters (address, size) are passed to an OS kernel that is
4020	being started.
4021   "Multi-File Images" contain several images, typically an OS
4022	(Linux) kernel image and one or more data images like
4023	RAMDisks. This construct is useful for instance when you want
4024	to boot over the network using BOOTP etc., where the boot
4025	server provides just a single image file, but you want to get
4026	for instance an OS kernel and a RAMDisk image.
4027
4028	"Multi-File Images" start with a list of image sizes, each
4029	image size (in bytes) specified by an "uint32_t" in network
4030	byte order. This list is terminated by an "(uint32_t)0".
4031	Immediately after the terminating 0 follow the images, one by
4032	one, all aligned on "uint32_t" boundaries (size rounded up to
4033	a multiple of 4 bytes).
4034
4035   "Firmware Images" are binary images containing firmware (like
4036	U-Boot or FPGA images) which usually will be programmed to
4037	flash memory.
4038
4039   "Script files" are command sequences that will be executed by
4040	U-Boot's command interpreter; this feature is especially
4041	useful when you configure U-Boot to use a real shell (hush)
4042	as command interpreter.
4043
4044Booting the Linux zImage:
4045-------------------------
4046
4047On some platforms, it's possible to boot Linux zImage. This is done
4048using the "bootz" command. The syntax of "bootz" command is the same
4049as the syntax of "bootm" command.
4050
4051Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4052kernel with raw initrd images. The syntax is slightly different, the
4053address of the initrd must be augmented by it's size, in the following
4054format: "<initrd addres>:<initrd size>".
4055
4056
4057Standalone HOWTO:
4058=================
4059
4060One of the features of U-Boot is that you can dynamically load and
4061run "standalone" applications, which can use some resources of
4062U-Boot like console I/O functions or interrupt services.
4063
4064Two simple examples are included with the sources:
4065
4066"Hello World" Demo:
4067-------------------
4068
4069'examples/hello_world.c' contains a small "Hello World" Demo
4070application; it is automatically compiled when you build U-Boot.
4071It's configured to run at address 0x00040004, so you can play with it
4072like that:
4073
4074	=> loads
4075	## Ready for S-Record download ...
4076	~>examples/hello_world.srec
4077	1 2 3 4 5 6 7 8 9 10 11 ...
4078	[file transfer complete]
4079	[connected]
4080	## Start Addr = 0x00040004
4081
4082	=> go 40004 Hello World! This is a test.
4083	## Starting application at 0x00040004 ...
4084	Hello World
4085	argc = 7
4086	argv[0] = "40004"
4087	argv[1] = "Hello"
4088	argv[2] = "World!"
4089	argv[3] = "This"
4090	argv[4] = "is"
4091	argv[5] = "a"
4092	argv[6] = "test."
4093	argv[7] = "<NULL>"
4094	Hit any key to exit ...
4095
4096	## Application terminated, rc = 0x0
4097
4098Another example, which demonstrates how to register a CPM interrupt
4099handler with the U-Boot code, can be found in 'examples/timer.c'.
4100Here, a CPM timer is set up to generate an interrupt every second.
4101The interrupt service routine is trivial, just printing a '.'
4102character, but this is just a demo program. The application can be
4103controlled by the following keys:
4104
4105	? - print current values og the CPM Timer registers
4106	b - enable interrupts and start timer
4107	e - stop timer and disable interrupts
4108	q - quit application
4109
4110	=> loads
4111	## Ready for S-Record download ...
4112	~>examples/timer.srec
4113	1 2 3 4 5 6 7 8 9 10 11 ...
4114	[file transfer complete]
4115	[connected]
4116	## Start Addr = 0x00040004
4117
4118	=> go 40004
4119	## Starting application at 0x00040004 ...
4120	TIMERS=0xfff00980
4121	Using timer 1
4122	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4123
4124Hit 'b':
4125	[q, b, e, ?] Set interval 1000000 us
4126	Enabling timer
4127Hit '?':
4128	[q, b, e, ?] ........
4129	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4130Hit '?':
4131	[q, b, e, ?] .
4132	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4133Hit '?':
4134	[q, b, e, ?] .
4135	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4136Hit '?':
4137	[q, b, e, ?] .
4138	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4139Hit 'e':
4140	[q, b, e, ?] ...Stopping timer
4141Hit 'q':
4142	[q, b, e, ?] ## Application terminated, rc = 0x0
4143
4144
4145Minicom warning:
4146================
4147
4148Over time, many people have reported problems when trying to use the
4149"minicom" terminal emulation program for serial download. I (wd)
4150consider minicom to be broken, and recommend not to use it. Under
4151Unix, I recommend to use C-Kermit for general purpose use (and
4152especially for kermit binary protocol download ("loadb" command), and
4153use "cu" for S-Record download ("loads" command).  See
4154https://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4155for help with kermit.
4156
4157
4158Nevertheless, if you absolutely want to use it try adding this
4159configuration to your "File transfer protocols" section:
4160
4161	   Name	   Program			Name U/D FullScr IO-Red. Multi
4162	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4163	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4164
4165
4166NetBSD Notes:
4167=============
4168
4169Starting at version 0.9.2, U-Boot supports NetBSD both as host
4170(build U-Boot) and target system (boots NetBSD/mpc8xx).
4171
4172Building requires a cross environment; it is known to work on
4173NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4174need gmake since the Makefiles are not compatible with BSD make).
4175Note that the cross-powerpc package does not install include files;
4176attempting to build U-Boot will fail because <machine/ansi.h> is
4177missing.  This file has to be installed and patched manually:
4178
4179	# cd /usr/pkg/cross/powerpc-netbsd/include
4180	# mkdir powerpc
4181	# ln -s powerpc machine
4182	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4183	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4184
4185Native builds *don't* work due to incompatibilities between native
4186and U-Boot include files.
4187
4188Booting assumes that (the first part of) the image booted is a
4189stage-2 loader which in turn loads and then invokes the kernel
4190proper. Loader sources will eventually appear in the NetBSD source
4191tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4192meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4193
4194
4195Implementation Internals:
4196=========================
4197
4198The following is not intended to be a complete description of every
4199implementation detail. However, it should help to understand the
4200inner workings of U-Boot and make it easier to port it to custom
4201hardware.
4202
4203
4204Initial Stack, Global Data:
4205---------------------------
4206
4207The implementation of U-Boot is complicated by the fact that U-Boot
4208starts running out of ROM (flash memory), usually without access to
4209system RAM (because the memory controller is not initialized yet).
4210This means that we don't have writable Data or BSS segments, and BSS
4211is not initialized as zero. To be able to get a C environment working
4212at all, we have to allocate at least a minimal stack. Implementation
4213options for this are defined and restricted by the CPU used: Some CPU
4214models provide on-chip memory (like the IMMR area on MPC8xx and
4215MPC826x processors), on others (parts of) the data cache can be
4216locked as (mis-) used as memory, etc.
4217
4218	Chris Hallinan posted a good summary of these issues to the
4219	U-Boot mailing list:
4220
4221	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4222	From: "Chris Hallinan" <clh@net1plus.com>
4223	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4224	...
4225
4226	Correct me if I'm wrong, folks, but the way I understand it
4227	is this: Using DCACHE as initial RAM for Stack, etc, does not
4228	require any physical RAM backing up the cache. The cleverness
4229	is that the cache is being used as a temporary supply of
4230	necessary storage before the SDRAM controller is setup. It's
4231	beyond the scope of this list to explain the details, but you
4232	can see how this works by studying the cache architecture and
4233	operation in the architecture and processor-specific manuals.
4234
4235	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4236	is another option for the system designer to use as an
4237	initial stack/RAM area prior to SDRAM being available. Either
4238	option should work for you. Using CS 4 should be fine if your
4239	board designers haven't used it for something that would
4240	cause you grief during the initial boot! It is frequently not
4241	used.
4242
4243	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4244	with your processor/board/system design. The default value
4245	you will find in any recent u-boot distribution in
4246	walnut.h should work for you. I'd set it to a value larger
4247	than your SDRAM module. If you have a 64MB SDRAM module, set
4248	it above 400_0000. Just make sure your board has no resources
4249	that are supposed to respond to that address! That code in
4250	start.S has been around a while and should work as is when
4251	you get the config right.
4252
4253	-Chris Hallinan
4254	DS4.COM, Inc.
4255
4256It is essential to remember this, since it has some impact on the C
4257code for the initialization procedures:
4258
4259* Initialized global data (data segment) is read-only. Do not attempt
4260  to write it.
4261
4262* Do not use any uninitialized global data (or implicitly initialized
4263  as zero data - BSS segment) at all - this is undefined, initiali-
4264  zation is performed later (when relocating to RAM).
4265
4266* Stack space is very limited. Avoid big data buffers or things like
4267  that.
4268
4269Having only the stack as writable memory limits means we cannot use
4270normal global data to share information between the code. But it
4271turned out that the implementation of U-Boot can be greatly
4272simplified by making a global data structure (gd_t) available to all
4273functions. We could pass a pointer to this data as argument to _all_
4274functions, but this would bloat the code. Instead we use a feature of
4275the GCC compiler (Global Register Variables) to share the data: we
4276place a pointer (gd) to the global data into a register which we
4277reserve for this purpose.
4278
4279When choosing a register for such a purpose we are restricted by the
4280relevant  (E)ABI  specifications for the current architecture, and by
4281GCC's implementation.
4282
4283For PowerPC, the following registers have specific use:
4284	R1:	stack pointer
4285	R2:	reserved for system use
4286	R3-R4:	parameter passing and return values
4287	R5-R10: parameter passing
4288	R13:	small data area pointer
4289	R30:	GOT pointer
4290	R31:	frame pointer
4291
4292	(U-Boot also uses R12 as internal GOT pointer. r12
4293	is a volatile register so r12 needs to be reset when
4294	going back and forth between asm and C)
4295
4296    ==> U-Boot will use R2 to hold a pointer to the global data
4297
4298    Note: on PPC, we could use a static initializer (since the
4299    address of the global data structure is known at compile time),
4300    but it turned out that reserving a register results in somewhat
4301    smaller code - although the code savings are not that big (on
4302    average for all boards 752 bytes for the whole U-Boot image,
4303    624 text + 127 data).
4304
4305On ARM, the following registers are used:
4306
4307	R0:	function argument word/integer result
4308	R1-R3:	function argument word
4309	R9:	platform specific
4310	R10:	stack limit (used only if stack checking is enabled)
4311	R11:	argument (frame) pointer
4312	R12:	temporary workspace
4313	R13:	stack pointer
4314	R14:	link register
4315	R15:	program counter
4316
4317    ==> U-Boot will use R9 to hold a pointer to the global data
4318
4319    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4320
4321On Nios II, the ABI is documented here:
4322	https://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4323
4324    ==> U-Boot will use gp to hold a pointer to the global data
4325
4326    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4327    to access small data sections, so gp is free.
4328
4329On NDS32, the following registers are used:
4330
4331	R0-R1:	argument/return
4332	R2-R5:	argument
4333	R15:	temporary register for assembler
4334	R16:	trampoline register
4335	R28:	frame pointer (FP)
4336	R29:	global pointer (GP)
4337	R30:	link register (LP)
4338	R31:	stack pointer (SP)
4339	PC:	program counter (PC)
4340
4341    ==> U-Boot will use R10 to hold a pointer to the global data
4342
4343NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4344or current versions of GCC may "optimize" the code too much.
4345
4346On RISC-V, the following registers are used:
4347
4348	x0: hard-wired zero (zero)
4349	x1: return address (ra)
4350	x2:	stack pointer (sp)
4351	x3:	global pointer (gp)
4352	x4:	thread pointer (tp)
4353	x5:	link register (t0)
4354	x8:	frame pointer (fp)
4355	x10-x11:	arguments/return values (a0-1)
4356	x12-x17:	arguments (a2-7)
4357	x28-31:	 temporaries (t3-6)
4358	pc:	program counter (pc)
4359
4360    ==> U-Boot will use gp to hold a pointer to the global data
4361
4362Memory Management:
4363------------------
4364
4365U-Boot runs in system state and uses physical addresses, i.e. the
4366MMU is not used either for address mapping nor for memory protection.
4367
4368The available memory is mapped to fixed addresses using the memory
4369controller. In this process, a contiguous block is formed for each
4370memory type (Flash, SDRAM, SRAM), even when it consists of several
4371physical memory banks.
4372
4373U-Boot is installed in the first 128 kB of the first Flash bank (on
4374TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4375booting and sizing and initializing DRAM, the code relocates itself
4376to the upper end of DRAM. Immediately below the U-Boot code some
4377memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4378configuration setting]. Below that, a structure with global Board
4379Info data is placed, followed by the stack (growing downward).
4380
4381Additionally, some exception handler code is copied to the low 8 kB
4382of DRAM (0x00000000 ... 0x00001FFF).
4383
4384So a typical memory configuration with 16 MB of DRAM could look like
4385this:
4386
4387	0x0000 0000	Exception Vector code
4388	      :
4389	0x0000 1FFF
4390	0x0000 2000	Free for Application Use
4391	      :
4392	      :
4393
4394	      :
4395	      :
4396	0x00FB FF20	Monitor Stack (Growing downward)
4397	0x00FB FFAC	Board Info Data and permanent copy of global data
4398	0x00FC 0000	Malloc Arena
4399	      :
4400	0x00FD FFFF
4401	0x00FE 0000	RAM Copy of Monitor Code
4402	...		eventually: LCD or video framebuffer
4403	...		eventually: pRAM (Protected RAM - unchanged by reset)
4404	0x00FF FFFF	[End of RAM]
4405
4406
4407System Initialization:
4408----------------------
4409
4410In the reset configuration, U-Boot starts at the reset entry point
4411(on most PowerPC systems at address 0x00000100). Because of the reset
4412configuration for CS0# this is a mirror of the on board Flash memory.
4413To be able to re-map memory U-Boot then jumps to its link address.
4414To be able to implement the initialization code in C, a (small!)
4415initial stack is set up in the internal Dual Ported RAM (in case CPUs
4416which provide such a feature like), or in a locked part of the data
4417cache. After that, U-Boot initializes the CPU core, the caches and
4418the SIU.
4419
4420Next, all (potentially) available memory banks are mapped using a
4421preliminary mapping. For example, we put them on 512 MB boundaries
4422(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4423on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4424programmed for SDRAM access. Using the temporary configuration, a
4425simple memory test is run that determines the size of the SDRAM
4426banks.
4427
4428When there is more than one SDRAM bank, and the banks are of
4429different size, the largest is mapped first. For equal size, the first
4430bank (CS2#) is mapped first. The first mapping is always for address
44310x00000000, with any additional banks following immediately to create
4432contiguous memory starting from 0.
4433
4434Then, the monitor installs itself at the upper end of the SDRAM area
4435and allocates memory for use by malloc() and for the global Board
4436Info data; also, the exception vector code is copied to the low RAM
4437pages, and the final stack is set up.
4438
4439Only after this relocation will you have a "normal" C environment;
4440until that you are restricted in several ways, mostly because you are
4441running from ROM, and because the code will have to be relocated to a
4442new address in RAM.
4443
4444
4445U-Boot Porting Guide:
4446----------------------
4447
4448[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4449list, October 2002]
4450
4451
4452int main(int argc, char *argv[])
4453{
4454	sighandler_t no_more_time;
4455
4456	signal(SIGALRM, no_more_time);
4457	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4458
4459	if (available_money > available_manpower) {
4460		Pay consultant to port U-Boot;
4461		return 0;
4462	}
4463
4464	Download latest U-Boot source;
4465
4466	Subscribe to u-boot mailing list;
4467
4468	if (clueless)
4469		email("Hi, I am new to U-Boot, how do I get started?");
4470
4471	while (learning) {
4472		Read the README file in the top level directory;
4473		Read https://www.denx.de/wiki/bin/view/DULG/Manual;
4474		Read applicable doc/README.*;
4475		Read the source, Luke;
4476		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4477	}
4478
4479	if (available_money > toLocalCurrency ($2500))
4480		Buy a BDI3000;
4481	else
4482		Add a lot of aggravation and time;
4483
4484	if (a similar board exists) {	/* hopefully... */
4485		cp -a board/<similar> board/<myboard>
4486		cp include/configs/<similar>.h include/configs/<myboard>.h
4487	} else {
4488		Create your own board support subdirectory;
4489		Create your own board include/configs/<myboard>.h file;
4490	}
4491	Edit new board/<myboard> files
4492	Edit new include/configs/<myboard>.h
4493
4494	while (!accepted) {
4495		while (!running) {
4496			do {
4497				Add / modify source code;
4498			} until (compiles);
4499			Debug;
4500			if (clueless)
4501				email("Hi, I am having problems...");
4502		}
4503		Send patch file to the U-Boot email list;
4504		if (reasonable critiques)
4505			Incorporate improvements from email list code review;
4506		else
4507			Defend code as written;
4508	}
4509
4510	return 0;
4511}
4512
4513void no_more_time (int sig)
4514{
4515      hire_a_guru();
4516}
4517
4518
4519Coding Standards:
4520-----------------
4521
4522All contributions to U-Boot should conform to the Linux kernel
4523coding style; see the kernel coding style guide at
4524https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4525script "scripts/Lindent" in your Linux kernel source directory.
4526
4527Source files originating from a different project (for example the
4528MTD subsystem) are generally exempt from these guidelines and are not
4529reformatted to ease subsequent migration to newer versions of those
4530sources.
4531
4532Please note that U-Boot is implemented in C (and to some small parts in
4533Assembler); no C++ is used, so please do not use C++ style comments (//)
4534in your code.
4535
4536Please also stick to the following formatting rules:
4537- remove any trailing white space
4538- use TAB characters for indentation and vertical alignment, not spaces
4539- make sure NOT to use DOS '\r\n' line feeds
4540- do not add more than 2 consecutive empty lines to source files
4541- do not add trailing empty lines to source files
4542
4543Submissions which do not conform to the standards may be returned
4544with a request to reformat the changes.
4545
4546
4547Submitting Patches:
4548-------------------
4549
4550Since the number of patches for U-Boot is growing, we need to
4551establish some rules. Submissions which do not conform to these rules
4552may be rejected, even when they contain important and valuable stuff.
4553
4554Please see https://www.denx.de/wiki/U-Boot/Patches for details.
4555
4556Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
4557see https://lists.denx.de/listinfo/u-boot
4558
4559When you send a patch, please include the following information with
4560it:
4561
4562* For bug fixes: a description of the bug and how your patch fixes
4563  this bug. Please try to include a way of demonstrating that the
4564  patch actually fixes something.
4565
4566* For new features: a description of the feature and your
4567  implementation.
4568
4569* For major contributions, add a MAINTAINERS file with your
4570  information and associated file and directory references.
4571
4572* When you add support for a new board, don't forget to add a
4573  maintainer e-mail address to the boards.cfg file, too.
4574
4575* If your patch adds new configuration options, don't forget to
4576  document these in the README file.
4577
4578* The patch itself. If you are using git (which is *strongly*
4579  recommended) you can easily generate the patch using the
4580  "git format-patch". If you then use "git send-email" to send it to
4581  the U-Boot mailing list, you will avoid most of the common problems
4582  with some other mail clients.
4583
4584  If you cannot use git, use "diff -purN OLD NEW". If your version of
4585  diff does not support these options, then get the latest version of
4586  GNU diff.
4587
4588  The current directory when running this command shall be the parent
4589  directory of the U-Boot source tree (i. e. please make sure that
4590  your patch includes sufficient directory information for the
4591  affected files).
4592
4593  We prefer patches as plain text. MIME attachments are discouraged,
4594  and compressed attachments must not be used.
4595
4596* If one logical set of modifications affects or creates several
4597  files, all these changes shall be submitted in a SINGLE patch file.
4598
4599* Changesets that contain different, unrelated modifications shall be
4600  submitted as SEPARATE patches, one patch per changeset.
4601
4602
4603Notes:
4604
4605* Before sending the patch, run the buildman script on your patched
4606  source tree and make sure that no errors or warnings are reported
4607  for any of the boards.
4608
4609* Keep your modifications to the necessary minimum: A patch
4610  containing several unrelated changes or arbitrary reformats will be
4611  returned with a request to re-formatting / split it.
4612
4613* If you modify existing code, make sure that your new code does not
4614  add to the memory footprint of the code ;-) Small is beautiful!
4615  When adding new features, these should compile conditionally only
4616  (using #ifdef), and the resulting code with the new feature
4617  disabled must not need more memory than the old code without your
4618  modification.
4619
4620* Remember that there is a size limit of 100 kB per message on the
4621  u-boot mailing list. Bigger patches will be moderated. If they are
4622  reasonable and not too big, they will be acknowledged. But patches
4623  bigger than the size limit should be avoided.
4624