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Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
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ReStructuredText
116 lines
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ReStructuredText
ARM Trusted Firmware for Socionext UniPhier SoCs
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================================================
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Socionext UniPhier ARMv8-A SoCs use ARM Trusted Firmware as the secure world
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firmware, supporting BL1, BL2, and BL31.
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UniPhier SoC family implements its internal boot ROM, so BL1 is used as pseudo
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ROM (i.e. runs in RAM). The internal boot ROM loads 64KB [1]_ image from a
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non-volatile storage to the on-chip SRAM. Unfortunately, BL1 does not fit in
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the 64KB limit if `Trusted Board Boot`_ (TBB) is enabled. To solve this problem,
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Socionext provides a first stage loader called `UniPhier BL`_. This loader runs
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in the on-chip SRAM, initializes the DRAM, expands BL1 there, and hands the
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control over to it. Therefore, all images of ARM Trusted Firmware run in DRAM.
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The UniPhier platform works with/without TBB. See below for the build process
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of each case. The image authentication for the UniPhier platform fully
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complies with the Trusted Board Boot Requirements (TBBR) specification.
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The UniPhier BL does not implement the authentication functionality, that is,
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it can not verify the BL1 image by itself. Instead, the UniPhier BL assures
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the BL1 validity in a different way; BL1 is GZIP-compressed and appended to
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the UniPhier BL. The concatenation of the UniPhier BL and the compressed BL1
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fits in the 64KB limit. The concatenated image is loaded by the boot ROM
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(and verified if the chip fuses are blown).
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Boot Flow
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---------
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1. The Boot ROM
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This is hard-wired ROM, so never corrupted. It loads the UniPhier BL (with
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compressed-BL1 appended) into the on-chip SRAM. If the SoC fuses are blown,
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the image is verified by the SoC's own method.
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2. UniPhier BL
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This runs in the on-chip SRAM. After the minimum SoC initialization and DRAM
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setup, it decompresses the appended BL1 image into the DRAM, then jumps to
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the BL1 entry.
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3. BL1
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This runs in the DRAM. It extracts BL2 from FIP (Firmware Image Package).
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If TBB is enabled, the BL2 is authenticated by the standard mechanism of ARM
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Trusted Firmware.
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4. BL2, BL31, and more
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They all run in the DRAM, and are authenticated by the standard mechanism if
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TBB is enabled. See `Firmware Design`_ for details.
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Basic Build
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-----------
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BL1 must be compressed for the reason above. The UniPhier's platform makefile
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provides a build target ``bl1_gzip`` for this.
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For a non-secure boot loader (aka BL33), U-Boot is well supported for UniPhier
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SoCs. The U-Boot image (``u-boot.bin``) must be built in advance. For the build
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procedure of U-Boot, refer to the document in the `U-Boot`_ project.
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To build minimum functionality for UniPhier (without TBB)::
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make CROSS_COMPILE=<gcc-prefix> PLAT=uniphier BL33=<path-to-BL33> bl1_gzip fip
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Output images:
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- ``bl1.bin.gzip``
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- ``fip.bin``
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Optional features
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-----------------
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- Trusted Board Boot
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`mbed TLS`_ is needed as the cryptographic and image parser modules.
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Refer to the `User Guide`_ for the appropriate version of mbed TLS.
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To enable TBB, add the following options to the build command::
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TRUSTED_BOARD_BOOT=1 GENERATE_COT=1 MBEDTLS_DIR=<path-to-mbedtls>
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- System Control Processor (SCP)
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If desired, FIP can include an SCP BL2 image. If BL2 finds an SCP BL2 image
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in FIP, BL2 loads it into DRAM and kicks the SCP. Most of UniPhier boards
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still work without SCP, but SCP provides better power management support.
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To include SCP BL2, add the following option to the build command::
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SCP_BL2=<path-to-SCP>
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- BL32 (Secure Payload)
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To enable BL32, add the following options to the build command::
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SPD=<spd> BL32=<path-to-BL32>
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If you use TSP for BL32, ``BL32=<path-to-BL32>`` is not required. Just add the
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following::
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SPD=tspd
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.. [1] Some SoCs can load 80KB, but the software implementation must be aligned
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to the lowest common denominator.
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.. _Trusted Board Boot: ../trusted-board-boot.rst
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.. _UniPhier BL: https://github.com/uniphier/uniphier-bl
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.. _Firmware Design: ../firmware-design.rst
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.. _U-Boot: https://www.denx.de/wiki/U-Boot
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.. _mbed TLS: https://tls.mbed.org/
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.. _User Guide: ../user-guide.rst
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