linux-kernel - Re: [PATCH v2] mmc: lower init clock frequency to 300kHz

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Message-ID: <20100102130809.121b7e10@mjolnir.ossman.eu>
Date:	Sat, 2 Jan 2010 13:08:09 +0100
From:	Pierre Ossman <pierre@...man.eu>
To:	Ben Nizette <bn@...sdigital.com>
Cc:	Hein_Tibosch <hein_tibosch@...oo.es>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Adrian Hunter <adrian.hunter@...ia.com>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Matt Fleming <matt@...sole-pimps.org>
Subject: Re: [PATCH v2] mmc: lower init clock frequency to 300kHz

On Sat, 2 Jan 2010 20:07:01 +1100
Ben Nizette <bn@...sdigital.com> wrote:

> 
> Pierre, thoughts?  All my cards were borderline spec but Hein's got a mainstream, common card which seems to completely ignore the spec.  Can we just take the few-hundred-uS hit and allow initialization down at the bottom end, say 100kHz?
> 

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.

Basically you'll just have to try something and watch the bug reports.
Perhaps doing the bisect approach and choosing the intermediate value
each time? I.e. halvway between 400 and 100 for now (250). If that is
too fast, then halway between that and 100 (175), and so on.

Rgds
-- 
     -- Pierre Ossman

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