[U-Boot] [PATCH 21/24] tegra124: Implement spl_was_boot_source()

[Simon Glass]

Hi Stephen,

On 5 May 2015 at 09:54, Stephen Warren <swarren at wwwdotorg.org> wrote:
> On 05/04/2015 11:31 AM, Simon Glass wrote:
>>
>> Add an implementation of this function for Tegra.
>
>
>> diff --git a/arch/arm/mach-tegra/board.c b/arch/arm/mach-tegra/board.c
>
>
>> +#ifndef CONFIG_SPL_BUILD
>> +void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3)
>> +{
>> +       from_spl = r0 != SPL_RUNNING_FROM_UBOOT;
>> +       save_boot_params_ret();
>> +}
>> +#endif
>
>
> (Using terminology from:
> https://patchwork.ozlabs.org/patch/467771/
> arm: spl: Enable detecting when U-Boot is started from SPL
> )
>
> That doesn't look right. Surely (at least on Tegra), if the r/o U-Boot
> chain-loads to the r/w U-Boot, then the chain-loaded U-Boot has no SPL and
> is just the main CPU build of U-Boot.
>
> Hence, "SPL_RUNNING_FROM_UBOOT" seems incorrectly named, since the r/o
> U-Boot doesn't chain to SPL but rather to U-Boot.

What name do you suggest? I was trying to add a prefix indicating that
it relates to non-SPL start-up of U-Boot.

>
> This approach sounds a little brittle; what happens if r0 just happens to
> have that value. Won't the code get confused?

Yes, but SPL does not set that value in r0, and we have control over this.

>
> Why does U-Boot care whether it's been chain-loaded? Shouldn't it always
> behave identically in all cases, so it's independent of what caused it to
> run?

In the case of read-only U-Boot it must find the read-write one to
jump to. In the case of read-write U-Boot it must boot a kernel.

Regards,
Simon