linux-kernel - Re: SDHCI: timeout during data transfer

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Date:	Mon, 20 Oct 2008 14:20:13 +0200
From:	"Luca Tettamanti" <kronos.it@...il.com>
To:	"Pierre Ossman" <drzeus-mmc@...eus.cx>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: SDHCI: timeout during data transfer

On Sat, Oct 18, 2008 at 10:46 PM, Pierre Ossman <drzeus-mmc@...eus.cx> wrote:
> On Tue, 14 Oct 2008 23:13:39 +0200
> "Luca Tettamanti" <kronos.it@...il.com> wrote:
>>
>> I finally managed to capture a failure with debug enabled, I'm
>> attaching the log.
>
> It seems to be a transfer error at least as it is in a completely
> different area of the card compared to the first mail you sent.
>
>> To recap:
>> - heavy write loads sometimes result in a timeout
>> - reads seem unaffected (I read the card multiple times without errors)
>
> Looking at the dump, the controller seems to be doing the correct
> thing. The timeout mandated by the SD specification is 250 ms, and that
> time has passed if you look at the timestamps. If you look at some
> other writes further down, the card takes around 220 ms for the writes.
> IOW, it would seem that this card is cutting it a bit close and
> sometimes goes over the alloted time.
>
>> - doubling the timeout (as per my first patch) makes the timeout disappear
>
> Since it is the card that's the problem here, not the controller, we'd
> need to fix this in the core. Unfortunately the sdhci hardware is a bit
> inflexible so any change I make will result in a doubling of the
> timeout.
>
> Could you try modifying line 283 of drivers/mmc/core/core.c where it
> says "limit_us = 250000;" to 300000 instead?

300ms seems to be enough.

>> I've tested two other cards that do not show the problem, but they are
>> not "high speed":
>>
>> mmc0: new high speed SD card at address 0002 (troubles)
>> vs:
>> mmc0: new SD card at address e624 (OK)
>
> What's the vendor and model of the failing card?

The card is from S3+, and it's branded "SD Excel" (el-cheapo 4GB card)

Luca
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