On Tue Jan 14, 2025 at 9:39 AM CET, Ahmad Fatoum wrote: > 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? Yeah i think it's better to remove irrelevant 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. only relevant for the PBL >> +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 Thanks, i'll take a look >> +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. yep, only relevant for PBL. >> +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. :-) Thanks for reading it :) > Cheers, > Ahmad
