[PATCH 7/7] doc: board/qualcomm: document rb3gen2 building/flashing

[Caleb Connolly]

The process here is almost identical to the Dragonboard 410c, we've come
full circle!

Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
---
 doc/board/qualcomm/rb3gen2.rst | 53 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/doc/board/qualcomm/rb3gen2.rst b/doc/board/qualcomm/rb3gen2.rst
new file mode 100644
index 000000000000..4240606224f5
--- /dev/null
+++ b/doc/board/qualcomm/rb3gen2.rst
@@ -0,0 +1,53 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. sectionauthor:: Caleb Connolly <caleb.connolly at linaro.org>
+
+Qualcomm Robotics RB3 Gen 2
+===========================
+
+The RB3 Gen 2 is a development board based on the Qualcomm QCM6490 SoC (a derivative
+of SC7280). More information can be found on `Qualcomm's product page`_.
+
+U-Boot can be used as a replacement for Qualcomm's original EDK2 bootloader by
+flashing it directly to the uefi_a (or _b) partition.
+
+.. _Qualcomm's product page: https://www.qualcomm.com/developer/hardware/rb3-gen-2-development-kit
+
+Installation
+------------
+First, setup ``CROSS_COMPILE`` for aarch64. Then, build U-Boot for ``qcm6490``::
+
+  $ export CROSS_COMPILE=<aarch64 toolchain prefix>
+  $ make qcm6490_defconfig
+  $ make -j8
+
+This will build ``u-boot.elf`` in the configured output directory.
+
+Although the RB3 Gen 2 does not have secure boot set up by default,
+the firmware still expects firmware ELF images to be "signed". The signature
+does not provide any security in this case, but it provides the firmware with
+some required metadata.
+
+To "sign" ``u-boot.elf`` you can use e.g. `qtestsign`_::
+
+  $ qtestsign -v6 aboot -o u-boot.mbn u-boot.elf
+
+Then install the resulting ``u-boot.mbn`` to the ``uefi_a`` partition
+on your device with ``fastboot flash uefi_a u-boot.mbn``.
+
+U-Boot should be running after a reboot (``fastboot reboot``).
+
+Note that fastboot is not yet supported in U-Boot on this board, as a result,
+to flash back the original firmware, or new versoins of the U-Boot, EDL mode
+must be used. This can be accessed by pressing the EDL mode button as described
+in the Qualcomm Linux documentation. A tool like bkerler's `edl`_ can be used
+for flashing with the firehose loader binary appropriate for the board.
+
+.. _qtestsign: https://github.com/msm8916-mainline/qtestsign
+.. _edl: https://github.com/bkerler/edl
+
+Usage
+-----
+
+The USB Type-A ports are connected via a PCIe USB hub, which is not supported yet.
+However, the Type-C port can be used with a powered USB dock to connect peripherals
+like a USB stick.

-- 
2.46.0