Re: [PATCH v3] mmc: Make ID freq configurable

[Hein_Tibosch]

Pierre Ossman wrote:
> On Sun, 3 Jan 2010 09:23:30 +1100
> Ben Nizette <bn@xxxxxxxxxxxxxxx> wrote:
>
>   
> > > Broken cards seem to be all over the spectrum, so I wouldn't be
> > > suprised if you find ones that break if you go too low as well.
> > >       
> > Yea good point, though given there might not even be a One Freq to Rule Them All, how about:
> >
> > ---8<---
> >
> > From: Ben Nizette <bn@xxxxxxxxxxxxxxx>
> > Subject: [PATCH v3] mmc: Make ID freq configurable
> >
> > While the SD spec specifies a range of frequencies for the ID phase from 100-400kHz, not all cards play by the rules.  This patch adds a Kconfig option to allow the user to tweak this to their card/host config, though the default of 250kHz should be fine for all spec-abiding cards and most others besides.
> >
> > Signed-off-by: Ben Nizette <bn@xxxxxxxxxxxxxxx>
> >
> >     
>
> This is not a good solution. We all use the same pool of cards so we
> should all be using the same init sequence. If there isn't a single
> frequency where all cards will work, then we'll have to make something
> more advanced where the kernel will try the init several times with
> different clocking.
>   
As I'm lucky to have main-stream cards that break the rule (on
avr32/AP7) I'll dive deeper into it and see if I can make it "automatic"
so that initialization will work for any of cards. Indeed using a kind
of 'bisect approach' approach.
... although I must say that before Sascha Hauer's patch, we never had
problems with any of the cards, using the controller's minimum freq of
137 Khz.

Hein



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