linux-kernel - Re: MMC: CRC Errors with 2GB cards

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Date:	Sat, 27 Oct 2007 14:00:17 +0200
From:	Pierre Ossman <drzeus-list@...eus.cx>
To:	Roopesh <roopesh@...erspace.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: MMC: CRC Errors with 2GB cards

Hi Roopesh,

I'm terribly sorry I haven't replied sooner. I put your message on my todo list, figuring I could get to it within a day or two, but as you noticed, that didn't quite happen. :/

On Fri, 19 Oct 2007 12:17:00 -0400
Roopesh <roopesh@...erspace.org> wrote:

>  Hi, 
> 
>  I am seeing a lot of CRC errors happening with CMD25 on a couple 
>  of Transcend 2GB cards (specifiation version 1.1).  However, if 
>  I apply the following patch, I see no errors being reported
> 

Ok, so the card is mishandling the state bits a bit. We should be able to work around that.

> @@ -310,8 +311,8 @@
>  					       req->rq_disk->disk_name, err);
>  					goto cmd_err;
>  				}
> -			} while (!(cmd.resp[0] & R1_READY_FOR_DATA));
> -
> +			} while (!(R1_CURRENT_STATE(cmd.resp[0]) == 4)); 
> +			
>  #if 0

This might trade us one problem for another. Could you try the following:

} while (!(cmd.resp[0] & R1_READY_FOR_DATA) || (R1_CURRENT_STATE(cmd.resp[0]) == 7));

This should also work for cards that mishandle the state field, and if the card jumps to
some odd state for some reason.

> 
>  I am just wondering if I have set of broken cards.  Any pointers 
>  in this regard?
> 

You do. But don't be too alarmed, that is unfortunately the norm. :/

Rgds
-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  PulseAudio, core developer          http://pulseaudio.org
  rdesktop, core developer          http://www.rdesktop.org
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