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+ARM Trusted Firmware for Socionext UniPhier SoCs
+================================================
+
+Socionext UniPhier ARMv8-A SoCs use ARM Trusted Firmware as the secure world
+firmware, supporting BL1, BL2, and BL31.
+
+UniPhier SoC family implements its internal boot ROM, so BL1 is used as pseudo
+ROM (i.e. runs in RAM). The internal boot ROM loads 64KB `1`_ image from a
+non-volatile storage to the on-chip SRAM. Unfortunately, BL1 does not fit in
+the 64KB limit if `Trusted Board Boot`_ (TBB) is enabled. To solve this problem,
+Socionext provides a first stage loader called `UniPhier BL`_. This loader runs
+in the on-chip SRAM, initializes the DRAM, expands BL1 there, and hands the
+control over to it. Therefore, all images of ARM Trusted Firmware 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 BL1 image by itself. Instead, the UniPhier BL assures
+the BL1 validity in a different way; BL1 is GZIP-compressed and appended to
+the UniPhier BL. The concatenation of the UniPhier BL and the compressed BL1
+fits in the 64KB limit. The concatenated image is loaded by the boot ROM
+(and verified if the chip fuses are blown).
+
+::
+
+     to the lowest common denominator.
+
+Boot Flow
+---------
+
+#. The Boot ROM
+
+This is hard-wired ROM, so never corrupted. It loads the UniPhier BL (with
+compressed-BL1 appended) into the on-chip SRAM. If the SoC fuses are blown,
+the image is verified by the SoC's own method.
+
+#. UniPhier BL
+
+This runs in the on-chip SRAM. After the minimum SoC initialization and DRAM
+setup, it decompresses the appended BL1 image into the DRAM, then jumps to
+the BL1 entry.
+
+#. BL1
+
+This runs in the DRAM. It extracts BL2 from FIP (Firmware Image Package).
+If TBB is enabled, the BL2 is authenticated by the standard mechanism of ARM
+Trusted Firmware.
+
+#. BL2, BL31, and more
+
+They all run in the DRAM, and are authenticated by the standard mechanism if
+TBB is enabled. See `Firmware Design`_ for details.
+
+Basic Build
+-----------
+
+BL1 must be compressed for the reason above. The UniPhier's platform makefile
+provides a build target ``bl1_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> bl1_gzip fip
+
+Output images:
+
+-  ``bl1.bin.gzip``
+-  ``fip.bin``
+
+Optional features
+-----------------
+
+-  Trusted Board Boot
+
+`mbed TLS`_ is needed as the cryptographic and image parser modules.
+Refer to the `User Guide`_ 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 option 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%20SoCs%20can%20load%2080KB,%20but%20the%20software%20implementation%20must%20be%20aligned
+.. _Trusted Board Boot: ../trusted-board-boot.rst
+.. _UniPhier BL: https://github.com/uniphier/uniphier-bl
+.. _Firmware Design: ../firmware-design.rst
+.. _U-Boot: https://www.denx.de/wiki/U-Boot
+.. _mbed TLS: https://tls.mbed.org/
+.. _User Guide: ../user-guide.rst