Hi Jules, On 07.01.25 15:37, Jules Maselbas wrote: > Add some informations about Allwinner sunxi boardsupport: the general > boot process, how to use sunxi-fel tool, and how to create a bootable > image disk. > > Signed-off-by: Jules Maselbas <jmaselbas@xxxxxxxx> Reviewed-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> with changes suggested below: > --- > Documentation/boards/sunxi.rst | 132 +++++++++++++++++++++++++++++++++ > 1 file changed, 132 insertions(+) > create mode 100644 Documentation/boards/sunxi.rst > > diff --git a/Documentation/boards/sunxi.rst b/Documentation/boards/sunxi.rst > new file mode 100644 > index 0000000000..46832559c9 > --- /dev/null > +++ b/Documentation/boards/sunxi.rst > @@ -0,0 +1,132 @@ > +.. > + SPDX-License-Identifier: GPL-2.0+ > + > + Copyright (C) 2022, Jules Maselbas > + > +Allwinner sunxi > +=============== > + > +Because of size constraints Barebox proper cannot boot directly, the uses > +of :doc:`PBL` allows to compress the Barebox image and it's device-tree. s/it's/its/ > +However this is not enough, and two images are acctually needed. The first s/acctually/actually/ > +image is suffixed *_xload* and it only consist of the PBL with a special > +entry point that looks for ``barebox.bin`` the root of a FAT partition. > +Only the SD card is currently searched, but this could also be in eMMC. > +The second image is your standard Barebox plus PBL image (suffixed ``.pblb``). The pblb image is just an intermediate artifact. There's usually an .img that's either 1:1 the pblb or the pblb with a SoC-specific header in front (or size patched in), so users need not mess with the pblb at all. Also, to avoid confusion, please add a note here that xload support isn't available yet or remove that part for now? > +eGON header > +----------- > + > +The eGON header structure is described in the file ``include/mach/sunxi/egon.h``. This file doesn't exist yet. > +This is also documented on https://linux-sunxi.org/EGON . > + > +The eGON header, followed by the actual image, must be located at the fixed > +offset of 8192 bytes (8KB) from the start of the disk (sector 16), either > +from SD card; or from eMMC. > + > +.. code-block:: sh > + > + # copy the "pine64_xload" eGON image into disk sdX > + dd if=images/start_pine64_pine64_xload.pblb.egonimg of=/dev/sdX bs=512 seek=16 > + > +The above will write the entire "pine64_xload" Barebox PBL plus the eGON > +header into the disk "/dev/sdX". > + > +The boot ROM will load, at most, the first 32KB of the image into SRAM, > +including the header itself! The eGON header starts with a jump instruction > +to jump over the header, this jump instruction needs to be patched accordingly > +with the header size. > + > +.. note:: > + > + On sunxi platforms the boot ROM loads the entire image **including** > + the eGON header. The actual base address will be offset by the eGON header > + (currently 96 bytes), this bad because arm instructions used for relocation s/this bad/this is bad/ > + expect the base address to be aligned on 4K boundary. > + As a workaround, a eGON header is included and linked into the Barebox > + PBL image, this dummy header will be filled later by egon_mkimage. Nice. > +Board images are defined in ``images/Makefile.sunxi``, here is an example:: > + > +.. code-block:: none > + > + pblb-$(CONFIG_MACH_PINE64_PINE64) += start_pine64_pine64_xload > + MAX_PBL_IMAGE_SIZE_start_pine64_pine64_xload = 0x8000 > + FILE_barebox-pine64-pine64_xload.img = start_pine64_pine64_xload.pblb.egonimg > + image-$(CONFIG_MACH_PINE64_PINE64) += barebox-pine64-pine64_xload.img While useful to have, I think the docs should start with user documentation first, i.e. a Building section that points out what defconfig to use, what images result and that only second stage is currently supported. See for example: https://www.barebox.org/doc/latest/boards/rockchip.html#id1 > +RMR aarch64 switch > +------------------ > + > +Aarch64 capable SoC (A64/sun50i) boot by default in 32-bit mode. A special header > +is added to the start of the PBL image in order to switch to aarch64 mode as soon > +as possible. This must be done very early in the boot process since both ISA are > +not compatible. The code to switch mode is already assembled (mostly arm 32bit) > +and is documented in the header file ``include/mach/sunxi/rmr_switch.h``. Likewise file doesn't exist yes. > +More documentation about FEL_ and how to use the sunxi-fel tool can be > +found on https://linux-sunxi.org/FEL/USBBoot . Is this already a clickable link? > +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:: > + > +.. code-block:: sh > + > + 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 > + cp build/sun50i_a64/debug/bl31.bin ${barebox_dir}/firmware/sun50i-a64-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. Thanks for taking the time to write such useful docs. :-) Cheers, Ahmad -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
