Re: [PATCH 0/4] rockchip: Improve support for Bob chromebook and add support for Kevin

[Alper Nebi Yasak <alpernebiyasak@gmail.com>]

On 08/12/2021 12:31, Peter Robinson wrote:
> I thought there was a different process for the chtomebooks than the
> usual rockchip route. Do the rockchip chomebooks support writing to a
> space in SPI and chainloading like some of the other arm chtomebooks
> did (I think tegra/samsung but my memory fades there)? I think it
> would be useful to document the rockchip chromebook options somewhere
> so that people that are interested in using the U-Boot option have
> some resources, we've had a few queries over the time around that.

What I usually do is exactly that, chainloading from an SPI region
called RW_LEGACY. This is the predecessor of the 'altfw' feature
mentioned in doc/chromium/overview.rst, there's a link there that leads
to some information about this as well. In short it goes like this:

- Build U-Boot with CONFIG_OF_EMBED=y
  (or do some objcopy/elfedit magic to merge dtb into u-boot ELF)
- cbfstool "u-boot.cbfs" create -s "$((2 * 1024 * 1024))" -m arm64
- cbfstool "u-boot.cbfs" add-payload -f "u-boot" -n payload -c lzma
- dd if="u-boot.cbfs" of="u-boot.cbfs.rom" bs=2M seek=3 count=1
- sudo flashrom -p linux_mtd --fmap -i RW_LEGACY -w "u-boot.cbfs.rom"
- Reboot and press CTRL+L on Chrome OS developer mode screen

There's also the doc/chromium/chainload.rst process which packs U-Boot
as if it's the Chrome OS kernel on a disk. I couldn't manage to boot
U-Boot that way, but I somewhat automated that process with binman. I
think I can automate the RW_LEGACY image as well but haven't tried it.

I could document what I know as is, but wanted to do it after I get
those files automated during upstream build, as things should be quite
simple after that.