[PATCH v3 10/22] passage: arm: Accept a passage from the previous phase

[Ilias Apalodimas]

Hi Simon,

On Thu, 17 Apr 2025 at 21:16, Simon Glass <sjg at chromium.org> wrote:
>
> Accept a bloblist and control devicetree from a previous phase in
> registers 0 to 3, as documented in the Firmware Handoff
> specification[1].
>
> [1] https://firmwarehandoff.github.io/firmware_handoff/main/index.html
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
> Changes in v3:
> - Add support for aarch64 also
> - Update registers to match the Firmware Handoff protocol
>
> Changes in v2:
> - Use three registers instead of two for the entry

[...]

> --- a/arch/arm/cpu/armv8/start.S
> +++ b/arch/arm/cpu/armv8/start.S
> @@ -57,6 +57,18 @@ reset:
>         b       save_boot_params
>  .globl save_boot_params_ret
>  save_boot_params_ret:
> +#if CONFIG_IS_ENABLED(PASSAGE_IN)
> +       # Keep passage information in case it is provided
> +       cmp     x2, #0
> +       bne     no_passage
> +       mov     x19, x1         /* mach */
> +       mov     x20, x0         /* dtb */
> +       mov     x21, x3         /* bloblist */

Those are already stored in saved_args. Can you explain on the commit
message why you need to preserve them in x19-x21 as well?

[...]

/Ilias