linux-kernel - Re: [PATCH] mvsdio: fix config failure with some high speed SDHC cards

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Message-ID: <20090527222622.6539d92f@mjolnir.ossman.eu>
Date:	Wed, 27 May 2009 22:26:22 +0200
From:	Pierre Ossman <pierre@...man.eu>
To:	Nicolas Pitre <nico@....org>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mvsdio: fix config failure with some high speed SDHC
 cards

On Tue, 26 May 2009 22:35:34 -0400 (EDT)
Nicolas Pitre <nico@....org> wrote:

>     
> Especially with Sandisk SDHC cards, the second SWITCH command was failing
> with a timeout and the card was not recognized at all.  However if the
> system was busy, or debugging was enabled, or a udelay(100) was inserted
> before the second SWITCH command in the core code, then the timing was
> so that the card started to work.
> 
> This appears to be a problem with the host hardware.  With some unusual
> block sizes, the data FIFO status doesn't indicate a "empty" state right
> away when the data transfer is done.  Queuing another data transfer in
> that condition results in a transfer timeout.
> 
> The empty FIFO bit eventually get set by itself in less than 50 usecs
> when it is not set right away. So let's just poll for that bit before
> configuring the controller with a new data transfer.
> 
> Signed-off-by: Nicolas Pitre <nico@...vell.com>
> 

You seem to be having a lot of fun with this controller. :)

Patch queued.

Rgds
-- 
     -- Pierre Ossman

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