[U-Boot] [PATCH 3/5] arm: Allow lr to be saved by board code

[Simon Glass]

Hi Albert,

On 4 February 2015 at 01:59, Albert ARIBAUD <albert.u.boot at aribaud.net> wrote:
> Hello Simon,
>
> On Tue,  3 Feb 2015 21:18:52 -0700, Simon Glass <sjg at chromium.org>
> wrote:
>> The link register value can be required on some boards (e.g. FEL mode on
>> sunxi) so stash it to r4 before jumping to save_boot_params().
>
> I'd rather not make this there; I would like save_boot_params to start
> with as unmodified a core state as possible, because r4 might
> actually, now or in the future, contain important data.
>
> I'd even go as far as saying that save_boot_params should be branched
> into rather than called, and should branch back to a fixed label right
> after reset, so that even lr is preserved. For SoCs which do not need
> to save any boot parameters, a weak version of save_boot_params would
> just do the branching back.
>
> (this should help merging all start.S instances into a singe one,
> which I still want to achieve one day)

I did consider this but was worried that some save_boot_params()
functions are written in C (OMAP) so this would not work. But if we
can require it to be written in assembler, or provide an asm macro to
return from the C function, then I can do that. What do you think?

Regards,
Simon