1Socionext UniPhier
2==================
3
4Socionext UniPhier Armv8-A SoCs use Trusted Firmware-A (TF-A) as the secure
5world firmware, supporting BL2 and BL31.
6
7UniPhier SoC family implements its internal boot ROM, which loads 64KB [1]_
8image from a non-volatile storage to the on-chip SRAM, and jumps over to it.
9TF-A provides a special mode, BL2-AT-EL3, which enables BL2 to execute at EL3.
10It is useful for platforms with non-TF-A boot ROM, like UniPhier. Here, a
11problem is BL2 does not fit in the 64KB limit if
12:ref:`Trusted Board Boot (TBB) <Trusted Board Boot>` is enabled.
13To solve this issue, Socionext provides a first stage loader called
14`UniPhier BL`_. This loader runs in the on-chip SRAM, initializes the DRAM,
15expands BL2 there, and hands the control over to it. Therefore, all images
16of TF-A run in DRAM.
17
18The UniPhier platform works with/without TBB. See below for the build process
19of each case. The image authentication for the UniPhier platform fully
20complies with the Trusted Board Boot Requirements (TBBR) specification.
21
22The UniPhier BL does not implement the authentication functionality, that is,
23it can not verify the BL2 image by itself. Instead, the UniPhier BL assures
24the BL2 validity in a different way; BL2 is GZIP-compressed and appended to
25the UniPhier BL. The concatenation of the UniPhier BL and the compressed BL2
26fits in the 64KB limit. The concatenated image is loaded by the internal boot
27ROM (and verified if the chip fuses are blown).
28
29
30Boot Flow
31---------
32
331. The Boot ROM
34
35   This is hard-wired ROM, so never corrupted. It loads the UniPhier BL (with
36   compressed-BL2 appended) into the on-chip SRAM. If the SoC fuses are blown,
37   the image is verified by the SoC's own method.
38
392. UniPhier BL
40
41   This runs in the on-chip SRAM. After the minimum SoC initialization and DRAM
42   setup, it decompresses the appended BL2 image into the DRAM, then jumps to
43   the BL2 entry.
44
453. BL2 (at EL3)
46
47   This runs in the DRAM. It extracts more images such as BL31, BL33 (optionally
48   SCP_BL2, BL32 as well) from Firmware Image Package (FIP). If TBB is enabled,
49   they are all authenticated by the standard mechanism of TF-A.
50   After loading all the images, it jumps to the BL31 entry.
51
524. BL31, BL32, and BL33
53
54   They all run in the DRAM. See :ref:`Firmware Design` for details.
55
56
57Basic Build
58-----------
59
60BL2 must be compressed for the reason above. The UniPhier's platform makefile
61provides a build target ``bl2_gzip`` for this.
62
63For a non-secure boot loader (aka BL33), U-Boot is well supported for UniPhier
64SoCs. The U-Boot image (``u-boot.bin``) must be built in advance. For the build
65procedure of U-Boot, refer to the document in the `U-Boot`_ project.
66
67To build minimum functionality for UniPhier (without TBB)::
68
69    make CROSS_COMPILE=<gcc-prefix> PLAT=uniphier BL33=<path-to-BL33> bl2_gzip fip
70
71Output images:
72
73- ``bl2.bin.gz``
74- ``fip.bin``
75
76
77Optional features
78-----------------
79
80- Trusted Board Boot
81
82  `mbed TLS`_ is needed as the cryptographic and image parser modules.
83  Refer to the :ref:`Prerequisites` document for the appropriate version of
84  mbed TLS.
85
86  To enable TBB, add the following options to the build command::
87
88      TRUSTED_BOARD_BOOT=1 GENERATE_COT=1 MBEDTLS_DIR=<path-to-mbedtls>
89
90- System Control Processor (SCP)
91
92  If desired, FIP can include an SCP BL2 image. If BL2 finds an SCP BL2 image
93  in FIP, BL2 loads it into DRAM and kicks the SCP. Most of UniPhier boards
94  still work without SCP, but SCP provides better power management support.
95
96  To include SCP BL2, add the following option to the build command::
97
98      SCP_BL2=<path-to-SCP>
99
100- BL32 (Secure Payload)
101
102  To enable BL32, add the following options to the build command::
103
104      SPD=<spd> BL32=<path-to-BL32>
105
106  If you use TSP for BL32, ``BL32=<path-to-BL32>`` is not required. Just add the
107  following::
108
109      SPD=tspd
110
111
112.. [1] Some SoCs can load 80KB, but the software implementation must be aligned
113   to the lowest common denominator.
114.. _UniPhier BL: https://github.com/uniphier/uniphier-bl
115.. _U-Boot: https://www.denx.de/wiki/U-Boot
116.. _mbed TLS: https://tls.mbed.org/
117