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SubjectRe: [PATCH] [OLPC] sdhci: add quirk for the Marvell CaFe's interrupt timeout
On Mon, 23 Jun 2008 10:13:52 -0400
Andres Salomon <dilinger@queued.net> wrote:

>
> The CaFe chip has a hardware bug that ends up with us getting a timeout
> value that's too small, causing the following sorts of problems:
>
> [ 60.525138] mmcblk0: error -110 transferring data
> [ 60.531477] end_request: I/O error, dev mmcblk0, sector 1484353
> [ 60.533371] Buffer I/O error on device mmcblk0p2, logical block 181632
> [ 60.533371] lost page write due to I/O error on mmcblk0p2
>
> Presumably this is an off-by-one error in the hardware. Incrementing
> the timeout count value that we stuff into the TIMEOUT_CONTROL register
> gets us a value that works. This bug was originally discovered by
> Pierre Ossman, I believe.
>
> [thanks to Robert Millan for proving that this was still a problem]
>
> Signed-off-by: Andres Salomon <dilinger@debian.org>

Hmm... I'm not entirely sure about the specifics of the workaround
here. It's likely that we'll have an off-by-minus-one in another
controller, and off-by-two in a third.

Perhaps we should just have "broken timeout" and set the timeout to
0xE. It doesn't cause any side-effects except that the user will have
to wait slightly longer for requests to fail if the card has decided to
crap out.

> @@ -479,6 +482,13 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_data *data)
> break;
> }
>
> + /*
> + * Compensate for an off-by-one error in the CaFe hardware; otherwise,
> + * a too-small count gives us interrupt timeouts.
> + */

Same issue with "CaFE" as the previous patch.

--
-- Pierre Ossman

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