[PATCH v4 10/10] doc: renesas: add Renesas board docs

[Ralph Siemsen]

Collect the list of currerently supported Renesas boards.

For the RZ/N1 board, add details about booting and flashing.

Signed-off-by: Ralph Siemsen <ralph.siemsen at linaro.org>
---

(no changes since v1)

 doc/board/renesas/index.rst   |   9 +++
 doc/board/renesas/renesas.rst | 115 ++++++++++++++++++++++++++++++++++
 2 files changed, 124 insertions(+)
 create mode 100644 doc/board/renesas/index.rst
 create mode 100644 doc/board/renesas/renesas.rst

diff --git a/doc/board/renesas/index.rst b/doc/board/renesas/index.rst
new file mode 100644
index 0000000000..3244c9d45e
--- /dev/null
+++ b/doc/board/renesas/index.rst
@@ -0,0 +1,9 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Renesas
+=======
+
+.. toctree::
+   :maxdepth: 2
+
+   renesas
diff --git a/doc/board/renesas/renesas.rst b/doc/board/renesas/renesas.rst
new file mode 100644
index 0000000000..5ae84004cf
--- /dev/null
+++ b/doc/board/renesas/renesas.rst
@@ -0,0 +1,115 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Renesas
+=======
+
+About this
+----------
+
+This document describes the information about Renesas supported boards
+and their usage steps.
+
+Renesas boards
+--------------
+
+Renesas is a SoC solutions provider for industrial applications.
+
+U-boot supports several Renesas SoC families:
+
+* rcar gen1/gen2 (32-bit)
+    - Blanche board
+    - Gose board
+    - Koelsch board
+    - Lager board
+    - Silk board
+    - Porter board
+    - Stout board
+* rcar gen3 (64-bit)
+    - Condor board
+    - Draak board
+    - Eagle board
+    - Ebisu board
+    - Falcon board
+    - Salvator-x board
+    - Ulcb board
+    - Beacon-rzg2 board
+    - Hihope-rzg2 board
+    - ek874 board
+* rza1 (32-bit)
+    - GR-PEACH board
+* rzn1 (32-bit)
+    - Schneider rzn1-snarc board
+
+Building
+--------
+
+NOTE: the following information is for the rzn1 board only.
+
+U-Boot
+^^^^^^
+
+Clone the u-boot repository and build it as follows:
+
+.. code-block:: bash
+
+        git clone --depth 1 https://source.denx.de/u-boot/u-boot.git
+        cd u-boot
+        make rzn1_snarc_defconfig
+        make CROSS_COMPILE=arm-linux-gnu-
+
+This produces `u-boot` which is an ELF executable, suitable for use with `gdb`
+and JTAG debugging tools.
+
+It also produceds `u-boot.bin` which is a raw binary.
+
+SPKG image
+^^^^^^^^^^
+
+The BootROM in the RZ/N1 SoC expects to find the boot image in SPKG format.
+This format is documented in Chapter 7.4 of the RZ/N1 User Manual.
+
+The raw u-boot binary can be wrapped into SPKG format as follows:
+
+.. code-block:: bash
+
+    tools/mkimage -n board/schneider/rzn1-snarc/spkgimage.cfg \
+            -T spkgimage -a 0x20040000 -e 0x20040000 \
+            -d u-boot.bin u-boot.bin.spkg
+
+This produces `u-boot.bin.spkg` which can be flashed into QSPI, NAND, or loaded
+via USB-DFU mode.
+
+Take note of the load and execution address, which are encoded into the SPKG
+headers. For development convenience, mkimage computes the execution offset
+(part of the SPKG header) by subtracting the supplied load address from the
+supplied execution address.
+
+Also note there are other parameters, notably ECC configuration in the case of
+boot from NAND, specified in the `spkgimage.cfg` configuration file.
+
+Binman
+^^^^^^
+
+Alternatively `binman` may be used to generate the SPKG format for booting.
+This tool and its pre-requisites must be installed as per
+:doc:`../../../tools/binman/binman.rst``
+
+.. code-block:: bash
+
+    binman -d arch/arm/dts/r9a06g032-rzn1-snarc.dtb -o <OUT>
+
+This will produce `u-boot.bin.spkg` in the specified <OUT> directory.
+
+Flashing
+--------
+
+The RZ/N1 is able to boot from QSPI, NAND, or via USB (DFU). In all cases the
+on-board BootROM expects for the binary to be wrapped with a "SPKG" header.
+This format is detailed in the RZ/N1 User Manual, and can be produced using
+the u-boot `mkimage` utility.
+
+It is possible to recover a bricked unit by using the USB (DFU) boot mode. This
+allows uploading u-boot into the internal RAM. Thereafter u-boot can be used to
+program the QSPI and/or NAND, making use of u-boot dfu mode.
+
+Otherwise the only other option for recovery is via JTAG.
-- 
2.25.1