[PATCH 2/2] vepxress64: add guide for running FVP with TF-A

[Harrison Mutai <harrison.mutai@arm.com>]

Add documentation on how to run FVP with U-Boot and TF-A. This helps
users configure and run U-Boot correctly on Arm models.

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
---
 doc/board/armltd/vexpress64.rst | 54 +++++++++++++++++++++++++++++++--
 1 file changed, 52 insertions(+), 2 deletions(-)

diff --git a/doc/board/armltd/vexpress64.rst b/doc/board/armltd/vexpress64.rst
index a732fac899d..434cc785bd6 100644
--- a/doc/board/armltd/vexpress64.rst
+++ b/doc/board/armltd/vexpress64.rst
@@ -19,6 +19,11 @@ view", which gives a comprehensive model on which to build and test software.
 The supported FVPs are available free of charge and can be downloaded from the
 Arm developer site [1]_ (user registration might be required).
 
+The Architecture Envelope Models (AEM) FVPs offer virtual platforms for Armv8-A,
+Armv9-A, and Armv8-R architectures, including a comprehensive set of System IP.
+For general use though, the Armv8-A Base Rev C FVP, which emulates a generic 64-bit
+Armv8-A hardware platform, is a suitable option.
+
 Supported features:
 
  * GICv3
@@ -31,6 +36,50 @@ into the TF-A build: ``make PLAT=<platform> all fip BL33=u-boot.bin``
 
 The FVPs can be debugged using Arm Development Studio [2]_.
 
+Building U-Boot
+^^^^^^^^^^^^^^^
+
+Set the ``CROSS_COMPILE`` environment variable as usual, and run:
+
+.. code-block:: bash
+
+    make vexpress_fvp_defconfig
+    make
+
+Running U-Boot
+^^^^^^^^^^^^^^
+
+Set ``CROSS_COMPILE`` as usual and build TF-A:
+
+.. code-block:: bash
+
+    git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
+    cd trusted-firmware-a
+    make PLAT=fvp BL33=/path/to/u-boot.bin fiptool all fip
+
+This command generates the ROM image `bl1.bin`, and a boot image `fip.bin` in
+TF-A's FIP format [5]. It contains all images executed by TF-A, including U-Boot.
+Note that TF-A outputs the built binaries into `build/fvp/release/`.
+
+If you already have a FIP image, and are primarily interested in updating the BL33
+image (i.e., U-Boot), use `fiptool` from TF-A:
+
+.. code-block:: bash
+
+    make fiptool
+    tools/fiptool/fiptool update --nt-fw=/path/to/u-boot.bin /path/to/fip.bin
+
+To run the FVP:
+
+.. code-block:: bash
+
+    FVP_Base_RevC-2xAEMvA -C bp.flashloader0.fname=fip.bin \
+        -C bp.secureflashloader.fname=bl1.bin \
+        -C bp.vis.disable_visualisation=1
+
+This setup relies on semi-hosting, as well as, having a kernel image (``Image``)
+and ramdisk (``ramdisk.img``) in the current working directory.
+
 Juno
 ----
 
@@ -62,7 +111,8 @@ tables.
 References
 ----------
 
-.. [1] https://developer.arm.com/tools-and-software/simulation-models/fixed-virtual-platforms
+.. [1] https://developer.arm.com/Tools%20and%20Software/Fixed%20Virtual%20Platforms/Arm%20Architecture%20FVPs
 .. [2] https://developer.arm.com/tools-and-software/embedded/arm-development-studio
 .. [3] https://developer.arm.com/tools-and-software/development-boards/juno-development-board
-.. [4] https://trustedfirmware-a.readthedocs.io/
\ No newline at end of file
+.. [4] https://trustedfirmware-a.readthedocs.io/
+.. [5] https://trustedfirmware-a.readthedocs.io/en/latest/getting_started/image-terminology.html#firmware-image-package-fip
-- 
2.46.2