1.. SPDX-License-Identifier: GPL-2.0+
2
3Android Fastboot
4================
5
6Overview
7--------
8
9The protocol that is used over USB and UDP is described in [1]_.
10
11The current implementation supports the following standard commands:
12
13- ``boot``
14- ``continue``
15- ``download``
16- ``erase`` (if enabled)
17- ``flash`` (if enabled)
18- ``getvar``
19- ``reboot``
20- ``reboot-bootloader``
21- ``set_active`` (only a stub implementation which always succeeds)
22- ``ucmd`` (if enabled)
23- ``acmd`` (if enabled)
24
25The following OEM commands are supported (if enabled):
26
27- ``oem format`` - this executes ``gpt write mmc %x $partitions``
28- ``oem partconf`` - this executes ``mmc partconf %x <arg> 0`` to configure eMMC
29  with <arg> = boot_ack boot_partition
30- ``oem bootbus``  - this executes ``mmc bootbus %x %s`` to configure eMMC
31
32Support for both eMMC and NAND devices is included.
33
34Client installation
35-------------------
36
37The counterpart to this is the fastboot client which can be found in
38Android's ``platform/system/core`` repository in the fastboot
39folder. It runs on Windows, Linux and OSX. The fastboot client is
40part of the Android SDK Platform-Tools and can be downloaded from [2]_.
41
42Board specific
43--------------
44
45USB configuration
46^^^^^^^^^^^^^^^^^
47
48The fastboot gadget relies on the USB download gadget, so the following
49options must be configured:
50
51::
52
53   CONFIG_USB_GADGET_DOWNLOAD
54   CONFIG_USB_GADGET_VENDOR_NUM
55   CONFIG_USB_GADGET_PRODUCT_NUM
56   CONFIG_USB_GADGET_MANUFACTURER
57
58NOTE: The ``CONFIG_USB_GADGET_VENDOR_NUM`` must be one of the numbers
59supported by the fastboot client. The list of vendor IDs supported can
60be found in the fastboot client source code.
61
62General configuration
63^^^^^^^^^^^^^^^^^^^^^
64
65The fastboot protocol requires a large memory buffer for
66downloads. This buffer should be as large as possible for a
67platform. The location of the buffer and size are set with
68``CONFIG_FASTBOOT_BUF_ADDR`` and ``CONFIG_FASTBOOT_BUF_SIZE``. These
69may be overridden on the fastboot command line using ``-l`` and
70``-s``.
71
72Fastboot environment variables
73------------------------------
74
75Partition aliases
76^^^^^^^^^^^^^^^^^
77
78Fastboot partition aliases can also be defined for devices where GPT
79limitations prevent user-friendly partition names such as ``boot``, ``system``
80and ``cache``.  Or, where the actual partition name doesn't match a standard
81partition name used commonly with fastboot.
82
83The current implementation checks aliases when accessing partitions by
84name (flash_write and erase functions).  To define a partition alias
85add an environment variable similar to::
86
87    fastboot_partition_alias_<alias partition name>=<actual partition name>
88
89for example::
90
91    fastboot_partition_alias_boot=LNX
92
93Raw partition descriptors
94^^^^^^^^^^^^^^^^^^^^^^^^^
95
96In cases where no partition table is present, a raw partition descriptor can be
97defined, specifying the offset, size, and optionally the MMC hardware partition
98number for a given partition name.
99
100This is useful when using fastboot to flash files (e.g. SPL or U-Boot) to a
101specific offset in the eMMC boot partition, without having to update the entire
102boot partition.
103
104To define a raw partition descriptor, add an environment variable similar to::
105
106    fastboot_raw_partition_<raw partition name>=<offset> <size> [mmcpart <num>]
107
108for example::
109
110    fastboot_raw_partition_boot=0x100 0x1f00 mmcpart 1
111
112Variable overrides
113^^^^^^^^^^^^^^^^^^
114
115Variables retrived through ``getvar`` can be overridden by defining
116environment variables of the form ``fastboot.<variable>``. These are
117looked up first so can be used to override values which would
118otherwise be returned. Using this mechanism you can also return types
119for NAND filesystems, as the fully parameterised variable is looked
120up, e.g.::
121
122    fastboot.partition-type:boot=jffs2
123
124Boot command
125^^^^^^^^^^^^
126
127When executing the fastboot ``boot`` command, if ``fastboot_bootcmd`` is set
128then that will be executed in place of ``bootm <CONFIG_FASTBOOT_BUF_ADDR>``.
129
130Partition Names
131---------------
132
133The Fastboot implementation in U-Boot allows to write images into disk
134partitions. Target partitions are referred on the host computer by
135their names.
136
137For GPT/EFI the respective partition name is used.
138
139For MBR the partitions are referred by generic names according to the
140following schema::
141
142    <device type><device index letter><partition index>
143
144Example: ``hda3``, ``sdb1``, ``usbda1``.
145
146The device type is as follows:
147
148  * IDE, ATAPI and SATA disks: ``hd``
149  * SCSI disks: ``sd``
150  * USB media: ``usbd``
151  * MMC and SD cards: ``mmcsd``
152  * Disk on chip: ``docd``
153  * other: ``xx``
154
155The device index starts from ``a`` and refers to the interface (e.g. USB
156controller, SD/MMC controller) or disk index. The partition index starts
157from ``1`` and describes the partition number on the particular device.
158
159Alternatively, partition types may be specified using :ref:`U-Boot's partition
160syntax <partitions>`. This allows specifying partitions like ``0.1``,
161``0#boot``, or ``:3``. The interface is always ``mmc``.
162
163Writing Partition Table
164-----------------------
165
166Fastboot also allows to write the partition table to the media. This can be
167done by writing the respective partition table image to a special target
168"gpt" or "mbr". These names can be customized by defining the following
169configuration options:
170
171::
172
173   CONFIG_FASTBOOT_GPT_NAME
174   CONFIG_FASTBOOT_MBR_NAME
175
176In Action
177---------
178
179Enter into fastboot by executing the fastboot command in U-Boot for either USB::
180
181   => fastboot usb 0
182
183or UDP::
184
185   => fastboot udp
186   link up on port 0, speed 100, full duplex
187   Using ethernet@4a100000 device
188   Listening for fastboot command on 192.168.0.102
189
190On the client side you can fetch the bootloader version for instance::
191
192   $ fastboot getvar version-bootloader
193   version-bootloader: U-Boot 2019.07-rc4-00240-g00c9f2a2ec
194   Finished. Total time: 0.005s
195
196or initiate a reboot::
197
198   $ fastboot reboot
199
200and once the client comes back, the board should reset.
201
202You can also specify a kernel image to boot. You have to either specify
203the an image in Android format *or* pass a binary kernel and let the
204fastboot client wrap the Android suite around it. On OMAP for instance you
205take zImage kernel and pass it to the fastboot client::
206
207   $ fastboot -b 0x80000000 -c "console=ttyO2 earlyprintk root=/dev/ram0 mem=128M" boot zImage
208   creating boot image...
209   creating boot image - 1847296 bytes
210   downloading 'boot.img'...
211   OKAY [  2.766s]
212   booting...
213   OKAY [ -0.000s]
214   finished. total time: 2.766s
215
216and on the U-Boot side you should see::
217
218   Starting download of 1847296 bytes
219   ........................................................
220   downloading of 1847296 bytes finished
221   Booting kernel..
222   ## Booting Android Image at 0x81000000 ...
223   Kernel load addr 0x80008000 size 1801 KiB
224   Kernel command line: console=ttyO2 earlyprintk root=/dev/ram0 mem=128M
225      Loading Kernel Image ... OK
226   OK
227
228   Starting kernel ...
229
230References
231----------
232
233.. [1] :doc:`fastboot-protocol`
234.. [2] https://developer.android.com/studio/releases/platform-tools
235