Messages in this thread | | | Date | Sun, 03 Jan 2010 16:00:09 +0800 | From | Hein_Tibosch <> | Subject | Re: [PATCH v3] mmc: Make ID freq configurable |
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Pierre Ossman wrote: > On Sun, 3 Jan 2010 09:23:30 +1100 > Ben Nizette <bn@niasdigital.com> 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@niasdigital.com> >> 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@niasdigital.com> >> >> > > 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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