[PATCH] sunxi: add board documentation

Andre Przywara andre.przywara at arm.com
Mon Dec 13 02:03:22 CET 2021

Add some long overdue instructions for building and installing U-Boot on
Allwinner SoC based boards.
This describes the building process, including TF-A and crust, plus
installation to SD card, eMMC and SPI flash, both from Linux and U-Boot
itself. Also describe FEL booting.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>

please have a look whether this makes sense. Feel free to just try something,
and point out ambiguities or missing bits. For missing topics, please
send a follow-up patch ;-)

Also this is quite long, shall this be split up in two (or more) files?

This is what rst.ninjs.org made of it, if you prefer to read it formatted:


 doc/board/allwinner/index.rst |   9 +
 doc/board/allwinner/sunxi.rst | 304 ++++++++++++++++++++++++++++++++++
 2 files changed, 313 insertions(+)
 create mode 100644 doc/board/allwinner/index.rst
 create mode 100644 doc/board/allwinner/sunxi.rst

diff --git a/doc/board/allwinner/index.rst b/doc/board/allwinner/index.rst
new file mode 100644
index 00000000000..7352ccd5c0a
--- /dev/null
+++ b/doc/board/allwinner/index.rst
@@ -0,0 +1,9 @@
+.. SPDX-License-Identifier: GPL-2.0+
+Allwinner (sunxi) boards
+.. toctree::
+   :maxdepth: 2
+   sunxi
diff --git a/doc/board/allwinner/sunxi.rst b/doc/board/allwinner/sunxi.rst
new file mode 100644
index 00000000000..693eb32e168
--- /dev/null
+++ b/doc/board/allwinner/sunxi.rst
@@ -0,0 +1,304 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright (C) 2021 Arm Ltd.
+Allwinner SoC based boards
+For boards using an Allwinner ARM based SoC ("sunxi"), the U-Boot build
+system generates a single integrated image file: ``u-boot-sunxi-with-spl.bin.``
+This file can be used on SD cards, eMMC devices, SPI flash and for the
+USB-OTG based boot method (FEL). To build this file:
+* For 64-bit SoCs, build Trusted Firmware (TF-A, formerly known as ATF) first,
+  you will need its ``bl31.bin``. See below for more details.
+* Optionally on 64-bit SoCs, build the crust management processor firmware.
+* Build U-Boot::
+  $ export BL31=/path/to/bl31.bin		# required for 64-bit SoCs
+  $ export SCP=/src/crust/build/scp/scp.bin	# optional for some 64-bit SoCs
+  $ make <yourboardname>_defconfig
+  $ make -j5 -s
+* Transfer to an uSD card (see below for more details)::
+  $ dd if=u-boot-sunxi-with-spl.bin of=/dev/sdX bs=8k seek=1
+* Boot and enjoy!
+For more details, and alternative boot locations or installations, see below.
+Building Arm Trusted Firmware (TF-A)
+Boards using a 64-bit Soc (A64, H5, H6, H616, R329) require the BL31 stage of
+the `Arm Trusted Firmware-A`_ firmware. This provides the reference
+implementation of secure software for Armv8-A, offering PSCI and SMCCC
+services. Allwinner support is fully mainlined. To build bl31.bin::
+  $ git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
+  $ cd trusted-firmware-a
+  $ make CROSS_COMPILE=aarch64-linux-gnu- PLAT=sun50i_a64 DEBUG=1
+  $ export BL31=$(pwd)/build/sun50i_a64/debug/bl31.bin
+The target platform (``PLAT=``) for A64 and H5 SoCs is sun50i_a64, for the H6
+sun50i_h6, for the H616 sun50i_h616, and for the R329 sun50i_r329. Use::
+  $ find plat/allwinner -name platform.mk
+to find all supported platforms. `docs/plat/allwinner.rst`_ contains more
+information and lists some build options.
+Building the Crust management processor firmware
+For some SoCs and boards, the integrated OpenRISC management controller can
+be used to provide power management services, foremost suspend to RAM.
+There is a community supported Open Source implementation called `crust`_,
+which runs on most SoCs featuring a management controller.
+This firmware part is optional, setting the SCP environment variable to
+/dev/null avoids the warning message when building without one.
+To build crust's scp.bin, you need an OpenRISC (or1k) cross compiler, then::
+  $ git clone https://github.com/crust-firmware/crust.git
+  $ cd crust
+  $ make <yourboard>_defconfig
+  $ make CROSS_COMPILE=or1k-none-elf- scp
+  $ export SCP=$(pwd)/build/scp/scp.bin
+Find a list of supported board configurations in the `configs/`_ directory.
+Building the U-Boot image
+Find the U-Boot defconfig file for your board first. Those files live in
+the ``configs/`` directory; you can grep for the stub name of the devicetree
+file, if you know that, or for the SoC name to find the right version::
+    $ git grep -l MACH_SUN8I_H3 configs
+    $ git grep -l sun50i-h6-orangepi-3 configs
+The `linux-sunxi`_ wiki also lists the name of the defconfig file in the
+respective board page. Then use this defconfig file to create the .config
+file, and build the image::
+    $ make <yourboard>_defconfig
+    $ make -j5
+For 64-bit boards, this requires either the BL31 environment variable to be
+set (as shown above in the TF-A build example), or it to be supplied on the
+build command line::
+    $ make BL31=/src/tf-a.git/build/sun50i_h616/debug/bl31.bin -j5 -s
+The same applies to the (optional) SCP firmware.
+The file containing everything you need is called ``u-boot-sunxi-with-spl.bin``,
+you will find it in the root folder of your U-Boot (build) tree. Except for
+raw NAND flash devices this very same file can be used for any boot source.
+It will contain the SPL image, fitted with the proper signature recognised by
+the BROM, and the required checksum. Also it will contain at least U-Boot
+proper, either wrapped in the legacy U-Boot image format, or in a FIT image.
+The board's devicetree is also included, either appended to the U-Boot proper
+image, or contained in the FIT image. If required by the SoC, this FIT file will
+also include the other firmware images.
+Installing U-Boot
+Installing on a (micro-) SD card
+All Allwinner SoCs will try to find a boot image at sector 16 (8KB) of
+an SD card, connected to the first MMC controller. To transfer the generated
+image to an SD card, from any Linux device (including the board itself) with
+an (micro-)SD card reader, type::
+    # dd if=u-boot-sunxi-with-spl.bin of=/dev/sdX bs=1k seek=8
+``/dev/sdx`` needs to be replaced with the block device name of the SD card
+reader. On some machines this could be ``/dev/mmcblkX``.
+Newer SoCs (starting from H3), also look at sector 256 (128KB) for the
+signature (after having checked the 8KB location). Installing the firmware
+there has the advantage of not overlapping with a GPT partition table. Simply
+replace the "``seek=8``" above with "``seek=128``".
+You can also use an existing (mainline) U-Boot to write to the SD card. Load
+the generated U-Boot image somewhere into DRAM (via ``ext4load``, ``fatload``,
+or ``tftpboot``), then write to MMC device 0::
+    => fatload mmc 0:1 $kernel_addr_r u-boot-sunxi-with-spl.bin
+    => mmc dev 0
+    => mmc write $kernel_addr_r 0x10 0x7f0
+To use the alternative boot location on newer SoCs::
+    => mmc write $kernel_addr_r 0x100 0x700
+Installing on eMMC (on-board flash memory)
+Some boards have a soldered eMMC chip, some other boards have an eMMC socket
+to receive an optional eMMC module. U-Boot can be installed to those chips,
+to boot without an SD card inserted. The Boot-ROM can boot either from the
+regular user data partition, or from one of the separate eMMC boot partitions.
+U-Boot can be installed either from a running Linux instance on the device,
+from a running (mainline) U-Boot, or via an adapter for the (removable)
+eMMC module.
+Installing on an eMMC user data partition from Linux
+If you have a running Linux instance on the device, and have somehow copied
+over the image file to that device, you can write the image directly into the
+eMMC device from there.
+Find the name of the block device file first, it is one of the
+``/dev/mmcblk<X>`` devices. eMMC devices typically also list a
+``/dev/mmcblk<X>boot0`` partition (see below), this helps you to tell it apart
+from the SD card device.
+To install onto the user data partition::
+    # dd if=u-boot-sunxi-with-spl.bin of=/dev/dev/mmcblkX bs=1k seek=8
+Similar to SD cards, the BROM in newer SoCs (H3 and above) also checks
+sector 256 of an eMMC, so you can use "``seek=128``" as well.
+Installing on an eMMC boot partition from Linux
+In the following examples, ``/dev/mmcblkX`` needs to be replaced with the block
+device name of the eMMC device. The eMMC device can be recognised by also
+listing the boot partitions (``/dev/mmcblkXboot0``) in ``/proc/partitions``.
+To allow booting from one of the eMMC boot partitions, this one needs to be
+enabled first. This only needs to be done once, as this setting is
+persistent, even though the boot partition can be disabled or changed again
+any time later::
+    # apt-get install mmc-utils
+    # mmc bootbus set single_hs x1 x4 /dev/mmcblkX
+    # mmc bootpart enable 1 1 /dev/mmcblkX
+The first "1" in the last command points to the boot partition number to be
+used, typically devices offer two boot partitions.
+By default Linux disables write access to the boot partitions, to prevent
+accidental overwrites. You need to disable the write protection (until the
+next reboot), then can write the U-Boot image to the *first* sector of the
+selected boot partition::
+    # echo 0 > /sys/block/mmcblkXboot0/force_ro
+    # dd if=u-boot-sunxi-with-spl.bin of=/dev/mmcblkXboot0 bs=1k
+Installing on an eMMC user data partition from U-Boot
+You can also write the generated image file to an SD card, boot the device
+from there, and burn the very same image to the eMMC device from U-Boot.
+The following commands copy the image from the SD card to the eMMC device::
+    => mmc dev 0
+    => mmc read $kernel_addr_r 0x10 0x7f0
+    => mmc dev 1
+    => mmc write $kernel_addr_r 0x10 0x7f0
+You can also copy an image from the 8K offset of an SD card to the 128K
+offset of the eMMC (or any combination), just change the "``0x10 0x7f0``" above
+to "``0x100 0x700``", respectively. Of course the image file can be loaded via
+any other loading method, including ``fatload``, ``ext4load``, ``tftpboot``.
+Installing on an eMMC boot partition from U-Boot
+The selected eMMC boot partition needs to be initially enabled first (same
+as in Linux above), you can do this from U-Boot with::
+    => mmc dev 1
+    => mmc bootbus 1 1 0 0
+    => mmc partconf 1 1 1 1
+The first "1" in both commands denotes the MMC device number. The second "1"
+in the partconf command sets the required ``BOOT_ACK`` option, the last two "1"s
+selects the active boot partition and the target for the next data access,
+respectively. So for the next "``mmc write``" command to address one of the boot
+partitions, the last number must either be "1" or "2", "0" would switch (back)
+to the normal user data partition.
+Then load the ``u-boot-sunxi-with-spl.bin`` image file into DRAM, either by
+reading directly from an SD card or eMMC user data partition, or from a
+file system or TFTP (see above), and transfer it to the boot partition::
+    => tftpboot $kernel_addr_r u-boot-sunxi-with-spl.bin
+    => mmc write $kernel_addr_r 0 0x7f0
+After that the device should boot from the selected boot partition, which takes
+precedence over booting from the user data partition.
+Installing on SPI flash
+Some devices have a SPI NOR flash chip soldered on the board. If it is
+connected to the SPI0 pins on PortC, the BROM can also boot from there.
+Typically the SPI flash has the lowest boot priority, so SD card and eMMC
+devices will be considered first.
+Installing on SPI flash from Linux
+If the devicetree enables and describes the SPI flash device, you can access
+the SPI flash content from Linux, using the `MTD utils`_::
+    # apt-get install mtd-utils
+    # mtdinfo
+    # mtd_debug erase /dev/mtdX 0 0xf0000
+    # mtd_debug write /dev/mtdX 0 0xf0000 u-boot-sunxi-with-spl.bin
+``/dev/mtdX`` needs to be replaced with the respective device name, as listed
+in the output of ``mtdinfo``.
+Installing on SPI flash from U-Boot
+If SPI flash driver and command support (``CONFIG_CMD_SF``) is enabled in the
+U-Boot configuration, the image file can be installed via U-Boot as well::
+    => tftpboot $kernel_addr_r u-boot-sunxi-with-spl.bin
+    => sf probe
+    => sf erase 0 +0xf0000
+    => sf write $kernel_addr_r 0 $filesize
+Installing on SPI flash via USB in FEL mode
+If the device is in FEL mode (see below), the SPI flash can also be filled
+with the sunxi-fel utility, via an USB(-OTG) cable from any USB host machine::
+    $ sunxi-fel -v -p spiflash-write 0 u-boot-sunxi-with-spl.bin
+Booting via the USB(-OTG) FEL mode
+If none of the boot locations checked by the BROM contain a medium or valid
+signature, the BROM will enter the so-called FEL mode, in which it will
+listen to commands from a host on the SoC's USB-OTG interface. Those commands
+allow to read from and write to arbitrary memory locations, also to start
+execution at any address, which allows to bootstrap a board solely via an
+USB cable. Some boards feature a "FEL" or "U-Boot" button, which forces
+FEL mode despite a valid boot location being present. The same can be achieved
+via a `magic binary`_ on an SD card, which allows to enter FEL mode on any
+To use FEL booting, let the board enter FEL mode, via any of the mentioned
+methods (no boot media, FEL button, SD card with FEL binary), then connect
+a USB cable to the board's USB OTG port. Some boards (Pine64, TV boxes) don't
+have a separate OTG port. In this case mostly one of the USB-A ports is
+connected to USB0, and can be used via a non-standard USB-A to USB-A cable.
+Typically there is no on-board indication of FEL mode, other than a new USB
+device appearing on the connected host computer. The USB vendor/device ID
+is 1f3a:efe8. Mostly this will identify as "sunxi SoC OTG connector in
+FEL/flashing mode", but older distributions might still report "Onda
+(unverified) V972 tablet in flashing mode".
+The `sunxi_fel`_ tool implements the proprietary BROM protocol, and allows to
+bootstrap U-Boot by just providing our venerable u-boot-sunxi-with-spl.bin::
+    $ sudo apt-get install sunxi-tools
+    $ sunxi-fel -v -p uboot u-boot-sunxi-with-spl.bin
+Additional binaries like a kernel, an initial ramdisk or a boot script, can
+also be uploaded via FEL, check the Wiki's `FEL page`_ for more details.
+.. _`Arm Trusted Firmware-A`:  https://www.trustedfirmware.org/projects/tf-a/
+.. _`docs/plat/allwinner.rst`: https://trustedfirmware-a.readthedocs.io/en/latest/plat/allwinner.html
+.. _`crust`: https://github.com/crust-firmware/crust
+.. _`configs/`: https://github.com/crust-firmware/crust/tree/master/configs
+.. _`linux-sunxi`: https://linux-sunxi.org
+.. _`MTD utils`: http://www.linux-mtd.infradead.org/
+.. _`magic binary`: https://github.com/linux-sunxi/sunxi-tools/raw/master/bin/fel-sdboot.sunxi
+.. _`sunxi_fel`: https://github.com/linux-sunxi/sunxi-tools
+.. _`FEL page`: https://linux-sunxi.org/FEL/USBBoot

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