On Tue, 29 Sep 2009 14:20:58 +0100 Matt Fleming <m...@console-pimps.org> wrote:
>
> I'm not sure that propagating this magical 400kHz constant around the
> MMC code is the best way to go. It could do with a #define.
>
> You're the second person to run into issues with the lower limit
> initialisation patch. Does anybody know where that value came from? Is
> it definitely the best value to use or has it just been picked out of
> the air?
The MMC and SD specs state that init must be done at < 400 kHz. We
originally used the lowest possible freq. the controller could handle,
but there was one controller who went so ridiculously low that it caused
other problems.
Re this patch, I'd think it would be more sensible to lower the init
frequency a bit than some retry logic. It is possible to init a card
and for it to end up in a weird state, so we should have margins
already at the first attempt.
Rgds
--
-- Pierre Ossman
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