[PATCH 3/3] doc: board: qualcomm: Document RUBIK Pi 3

[Hongyang Zhao]

Add build and flashing instructions for running U-Boot on the
Thundercomm RUBIK Pi 3 and include the page in the Qualcomm board
documentation index.

Signed-off-by: Hongyang Zhao <hongyang.zhao at thundersoft.com>
---
 doc/board/qualcomm/index.rst    |  1 +
 doc/board/qualcomm/rubikpi3.rst | 51 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/doc/board/qualcomm/index.rst b/doc/board/qualcomm/index.rst
index 3238a68e859..5bd9714d927 100644
--- a/doc/board/qualcomm/index.rst
+++ b/doc/board/qualcomm/index.rst
@@ -11,6 +11,7 @@ Qualcomm
    dragonboard410c
    dragonwing
    rb3gen2
+   rubikpi3
    iq8
    phones
    rdp
diff --git a/doc/board/qualcomm/rubikpi3.rst b/doc/board/qualcomm/rubikpi3.rst
new file mode 100644
index 00000000000..4ef60ddf536
--- /dev/null
+++ b/doc/board/qualcomm/rubikpi3.rst
@@ -0,0 +1,51 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. sectionauthor:: Hongyang Zhao <hongyang.zhao at thundersoft.com>
+
+Thundercomm RUBIK Pi 3
+======================
+
+The RUBIK Pi 3 is a development board based on the Qualcomm QCS6490 SoC,
+with 8 GiB LPDDR4x memory and 128 GiB UFS 2.2 storage. More information
+can be found on `Thundercomm'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 ``uefi_b``) partition.
+
+.. _Thundercomm's product page: https://www.thundercomm.com/rubik-pi-3/en/docs/about-rubikpi/
+
+Installation
+------------
+
+First, set up ``CROSS_COMPILE`` for aarch64. Then, build U-Boot for
+``qcs6490_rubikpi3``::
+
+  $ export CROSS_COMPILE=<aarch64 toolchain prefix>
+  $ make qcs6490_rubikpi3_defconfig
+  $ make -j8
+
+This will build ``u-boot.elf`` in the configured output directory.
+
+Although the RUBIK Pi 3 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 may not be available after replacing the original firmware.
+To restore the original firmware, or to install a new version of U-Boot, EDL
+mode can be used with the firehose loader binary appropriate for the board.
+
+A tool like bkerler's `edl`_ can be used for flashing::
+
+  $ edl.py --loader /path/to/prog_firehose_ddr.elf w uefi_a u-boot.mbn
+
+.. _qtestsign: https://github.com/msm8916-mainline/qtestsign
+.. _edl: https://github.com/bkerler/edl

-- 
2.43.0