118 lines
4.1 KiB
ReStructuredText
118 lines
4.1 KiB
ReStructuredText
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Socionext UniPhier
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==================
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Socionext UniPhier Armv8-A SoCs use Trusted Firmware-A (TF-A) as the secure
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world firmware, supporting BL2 and BL31.
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UniPhier SoC family implements its internal boot ROM, which loads 64KB [1]_
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image from a non-volatile storage to the on-chip SRAM, and jumps over to it.
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TF-A provides a special mode, BL2-AT-EL3, which enables BL2 to execute at EL3.
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It is useful for platforms with non-TF-A boot ROM, like UniPhier. Here, a
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problem is BL2 does not fit in the 64KB limit if `Trusted Board Boot`_ (TBB)
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is enabled. To solve this issue, Socionext provides a first stage loader
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called `UniPhier BL`_. This loader runs in the on-chip SRAM, initializes the
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DRAM, expands BL2 there, and hands the control over to it. Therefore, all images
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of TF-A 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 BL2 image by itself. Instead, the UniPhier BL assures
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the BL2 validity in a different way; BL2 is GZIP-compressed and appended to
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the UniPhier BL. The concatenation of the UniPhier BL and the compressed BL2
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fits in the 64KB limit. The concatenated image is loaded by the internal boot
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ROM (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-BL2 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 BL2 image into the DRAM, then jumps to
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the BL2 entry.
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3. BL2 (at EL3)
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This runs in the DRAM. It extracts more images such as BL31, BL33 (optionally
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SCP_BL2, BL32 as well) from Firmware Image Package (FIP). If TBB is enabled,
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they are all authenticated by the standard mechanism of TF-A.
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After loading all the images, it jumps to the BL31 entry.
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4. BL31, BL32, and BL33
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They all run in the DRAM. See `Firmware Design`_ for details.
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Basic Build
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-----------
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BL2 must be compressed for the reason above. The UniPhier's platform makefile
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provides a build target ``bl2_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> bl2_gzip fip
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Output images:
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- ``bl2.bin.gz``
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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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