[U-Boot] [PATCH 06/12 v2] arm: at91: Enable watchdog support

[Stefan Roese]

Hi Wolfgang,

On 29.03.19 13:06, Wolfgang Denk wrote:
> In message <81e69dec-21e7-7b34-a261-e22ae9bef795 at denx.de> you wrote:
>>
>> The big question is, how many places do we have in code, where we access
>> BSS before relocation ?
> 
> Hopefully none.
> 
>> May we better clear BSS very early (at last may possible on arm)?
> 
> You cannot.  There is no storage allocated for BSS - this happens
> only during relocation, and then it also gets zeroed.

This is not 100% correct for all platforms. On some targets, e.g.
where the DDR is initialized by SPL, the BSS location before
relocation is already a valid address space in DDR in the main
U-Boot proper. AFAICT, the BSS *could* already be used before
relocation in these cases. Here the BBS could be cleared very
early and relocated later with the code etc. No clearing in the
relocation stage necessary.

But since this is a special case, it makes no real sense to
implement such an "early BSS" strategy into U-Boot, as other
platforms will always exist, where the BSS is really only
available after relocation (as you mentioned above).

Thanks,
Stefan