[PATCH 2/2] board: stemmy: Copy atags for booting downstream/vendor kernel

[Linus Walleij]

On Wed, Jul 7, 2021 at 12:59 PM Stephan Gerhold <stephan at gerhold.net> wrote:

> The U-Boot "stemmy" board is mainly intended to simplify booting
> mainline Linux on various smartphones from Samsung based on ST-Ericsson
> Ux500. While the mainline kernel is working great, there are still some
> features missing there. In particular, it is currently not possible to
> charge the battery when using the mainline kernel.
>
> This means that it is still necessary to boot the downstream/vendor
> kernel from Samsung sometimes to charge the device. That kernel is
> ancient, still uses board files + ATAGS instead of device trees and
> relies on a strange very long kernel command line hardcoded in the
> Samsung bootloader.
>
> Actually, since mainline is booted with device trees there is a very
> simple way to make the old downstream kernel work as well: We can
> simply take most of the ATAGS passed to U-Boot from the Samsung
> bootloader and copy them as-is when booting a kernel without device
> tree. That way the long command line and other needed ATAGS are copied
> as-is without having to bother with them.
>
> The only exception is the ATAG_INITRD - since the initrd is loaded
> by U-Boot, the atag for that should be generated in U-Boot so it points
> to the correct address. All other ATAGS are copied as-is and not
> generated in U-Boot.
>
> Also use the chance and provide a serial# for U-Boot by parsing the
> ATAG_SERIAL that is also passed by the Samsung bootloader.
>
> Signed-off-by: Stephan Gerhold <stephan at gerhold.net>

Reviewed-by: Linus Walleij <linus.walleij at linaro.org>

Yours,
Linus Walleij