doc: board: renesas: Document Renesas R-Car Gen3 M3Le Geist board

Add document which clarifies how to build and install U-Boot on
Renesas R-Car Gen3 M3Le Geist board.

Include Renesas R-Car Gen3 SPI NOR installation procedure document.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

doc/board/renesas/index.rst

@@ -12,6 +12,8 @@ Renesas
    build-env-aarch64
    rcar-gen3-salvator-x
    rcar-gen3-ulcb
+   rcar-gen3-geist
    rcar-gen3-install
    rcar-gen3-install-hf
+   rcar-gen3-install-sf
    rzn1

doc/board/renesas/rcar-gen3-geist.rst

@@ -0,0 +1,45 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Renesas R-Car Gen3 M3Le Geist board
+===================================
+
+Build U-Boot
+------------
+
+Please follow :doc:`Renesas 64-bit ARM SoC build environment setup <build-env-aarch64>`
+to correctly set up the build environment before attempting to build U-Boot.
+
+Clone up to date U-Boot source code and change directory into the
+newly cloned source directory:
+
+.. code-block:: console
+
+    $ git clone https://source.denx.de/u-boot/u-boot.git/
+    $ cd u-boot
+
+Configure U-Boot:
+
+.. code-block:: console
+
+    $ make r8a779md_geist_defconfig
+
+Compile U-Boot:
+
+.. code-block:: console
+
+    $ make
+
+To speed up build process, -jN option can be passed to make to start
+multiple jobs at the same time, this is beneficial especially on SMP
+systems. The following example starts up to number of CPUs in the
+system jobs, which is the recommended amount:
+
+.. code-block:: console
+
+    $ make -j$(nproc)
+
+Install U-Boot
+--------------
+
+Please follow :doc:`Renesas R-Car Gen3 U-Boot installation <rcar-gen3-install>`
+to install U-Boot into SPI NOR.

doc/board/renesas/rcar-gen3-install-sf.rst

@@ -0,0 +1,29 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Renesas R-Car Gen3 U-Boot SPI NOR installation
+==============================================
+
+U-Boot can be installed on R-Car Gen3 systems into SPI NOR from U-Boot.
+
+.. note::
+
+    This update mechanism is only available in case the TFA has been built
+    with `RCAR_RPC_HYPERFLASH_LOCKED=0 SPD=none`.
+
+Install U-Boot into SPI NOR using write from U-Boot
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In order to install U-Boot using write into SPI NOR, first build U-Boot
+for this target and collect ``u-boot.bin`` build artifact. Then start the
+target, drop into U-Boot shell, and load the build artifact into DRAM at
+well known address:
+
+.. code-block:: console
+
+    => tftp 0x50000000 u-boot.bin
+
+Finally, write U-Boot into SPI NOR:
+
+.. code-block:: console
+
+    => sf probe && sf update 0x50000000 0x640000 $filesize

doc/board/renesas/rcar-gen3-install.rst

@@ -13,6 +13,10 @@ Installation into the HyperFlash can be performed from U-Boot, please
 refer to :doc:`Renesas R-Car Gen3 U-Boot HyperFlash installation <rcar-gen3-install-hf>`
 for details.
 
+Installation into the SPI NOR can be performed from U-Boot, please
+refer to :doc:`Renesas R-Car Gen3 U-Boot SPI NOR installation <rcar-gen3-install-sf>`
+for details.
+
 .. note::
 
     The maximum u-boot.bin size for this target is 1 MiB or 0x100000 Bytes

doc/board/renesas/renesas.rst

@@ -121,7 +121,7 @@ Renesas is a SoC solutions provider for automotive and industrial applications.
      - rcar3_ulcb_defconfig
 
    * -
-     - Geist
+     - :doc:`Geist <rcar-gen3-geist>`
      - R8A779MD (M3Le)
      - :doc:`arm64 <build-env-aarch64>`
      - r8a779md_geist_defconfig