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diff --git a/docs/plat/socionext-uniphier.rst b/docs/plat/socionext-uniphier.rst new file mode 100644 index 0000000..9288193 --- /dev/null +++ b/docs/plat/socionext-uniphier.rst @@ -0,0 +1,116 @@ +Socionext UniPhier +================== + +Socionext UniPhier Armv8-A SoCs use Trusted Firmware-A (TF-A) as the secure +world firmware, supporting BL2 and BL31. + +UniPhier SoC family implements its internal boot ROM, which loads 64KB [1]_ +image from a non-volatile storage to the on-chip SRAM, and jumps over to it. +TF-A provides a special mode, BL2-AT-EL3, which enables BL2 to execute at EL3. +It is useful for platforms with non-TF-A boot ROM, like UniPhier. Here, a +problem is BL2 does not fit in the 64KB limit if +:ref:`Trusted Board Boot (TBB) <Trusted Board Boot>` is enabled. +To solve this issue, Socionext provides a first stage loader called +`UniPhier BL`_. This loader runs in the on-chip SRAM, initializes the DRAM, +expands BL2 there, and hands the control over to it. Therefore, all images +of TF-A run in DRAM. + +The UniPhier platform works with/without TBB. See below for the build process +of each case. The image authentication for the UniPhier platform fully +complies with the Trusted Board Boot Requirements (TBBR) specification. + +The UniPhier BL does not implement the authentication functionality, that is, +it can not verify the BL2 image by itself. Instead, the UniPhier BL assures +the BL2 validity in a different way; BL2 is GZIP-compressed and appended to +the UniPhier BL. The concatenation of the UniPhier BL and the compressed BL2 +fits in the 64KB limit. The concatenated image is loaded by the internal boot +ROM (and verified if the chip fuses are blown). + + +Boot Flow +--------- + +1. The Boot ROM + + This is hard-wired ROM, so never corrupted. It loads the UniPhier BL (with + compressed-BL2 appended) into the on-chip SRAM. If the SoC fuses are blown, + the image is verified by the SoC's own method. + +2. UniPhier BL + + This runs in the on-chip SRAM. After the minimum SoC initialization and DRAM + setup, it decompresses the appended BL2 image into the DRAM, then jumps to + the BL2 entry. + +3. BL2 (at EL3) + + This runs in the DRAM. It extracts more images such as BL31, BL33 (optionally + SCP_BL2, BL32 as well) from Firmware Image Package (FIP). If TBB is enabled, + they are all authenticated by the standard mechanism of TF-A. + After loading all the images, it jumps to the BL31 entry. + +4. BL31, BL32, and BL33 + + They all run in the DRAM. See :ref:`Firmware Design` for details. + + +Basic Build +----------- + +BL2 must be compressed for the reason above. The UniPhier's platform makefile +provides a build target ``bl2_gzip`` for this. + +For a non-secure boot loader (aka BL33), U-Boot is well supported for UniPhier +SoCs. The U-Boot image (``u-boot.bin``) must be built in advance. For the build +procedure of U-Boot, refer to the document in the `U-Boot`_ project. + +To build minimum functionality for UniPhier (without TBB):: + + make CROSS_COMPILE=<gcc-prefix> PLAT=uniphier BL33=<path-to-BL33> bl2_gzip fip + +Output images: + +- ``bl2.bin.gz`` +- ``fip.bin`` + + +Optional features +----------------- + +- Trusted Board Boot + + `mbed TLS`_ is needed as the cryptographic and image parser modules. + Refer to the :ref:`Prerequisites` document for the appropriate version of + mbed TLS. + + To enable TBB, add the following options to the build command:: + + TRUSTED_BOARD_BOOT=1 GENERATE_COT=1 MBEDTLS_DIR=<path-to-mbedtls> + +- System Control Processor (SCP) + + If desired, FIP can include an SCP BL2 image. If BL2 finds an SCP BL2 image + in FIP, BL2 loads it into DRAM and kicks the SCP. Most of UniPhier boards + still work without SCP, but SCP provides better power management support. + + To include SCP BL2, add the following option to the build command:: + + SCP_BL2=<path-to-SCP> + +- BL32 (Secure Payload) + + To enable BL32, add the following options to the build command:: + + SPD=<spd> BL32=<path-to-BL32> + + If you use TSP for BL32, ``BL32=<path-to-BL32>`` is not required. Just add the + following:: + + SPD=tspd + + +.. [1] Some SoCs can load 80KB, but the software implementation must be aligned + to the lowest common denominator. +.. _UniPhier BL: https://github.com/uniphier/uniphier-bl +.. _U-Boot: https://www.denx.de/wiki/U-Boot +.. _mbed TLS: https://tls.mbed.org/ |