linux-kernel - Re: [PATCH 2/7] mmc_spi: wait more bytes for card response

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Date:	Wed, 11 Mar 2009 12:05:20 -0800
From:	David Brownell <david-b@...bell.net>
To:	Wolfgang Mües <wolfgang.mues@...rswald.de>
Cc:	Pierre Ossman <drzeus@...eus.cx>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Matt Fleming" <matt@...sole-pimps.org>,
	"Mike Frysinger" <vapier.adi@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] mmc_spi: wait more bytes for card response

On Wednesday 11 March 2009, Wolfgang Mües wrote:
> From: Wolfgang Muees <wolfgang.mues@...rswald.de>
> 
> o some cards are slower than the standard allows and need more
>   time to respond to a command. Max. observed number of bytes
>   was 12.
> 
> Signed-off-by: Wolfgang Muees <wolfgang.mues@...rswald.de>

Acked-by: David Brownell <dbrownell@...rs.sourceforge.net>

> 
> ---
> This is one of a line of patches to enhance the usability of
> the mmc spi host port driver from "don't work with most SD cards"
> to "work with nearly all SD cards" (including those ugly cards
> with non-byte-aligned responses).
> 
> diff -uprN 2_6_29_rc7_patch1_spi_mode_3/drivers/mmc/host/mmc_spi.c 2_6_29_rc7_patch2_wait_16bytes_response/drivers/mmc/host/mmc_spi.c
> --- 2_6_29_rc7_patch1_spi_mode_3/drivers/mmc/host/mmc_spi.c	2009-03-11 12:58:47.000000000 +0100
> +++ 2_6_29_rc7_patch2_wait_16bytes_response/drivers/mmc/host/mmc_spi.c	2009-03-11 13:00:06.000000000 +0100
> @@ -279,8 +279,11 @@ static int mmc_spi_response_get(struct m
>  		 * so it can always DMA directly into the target buffer.
>  		 * It'd probably be better to memcpy() the first chunk and
>  		 * avoid extra i/o calls...
> +		 *
> +		 * Note we check for more than 8 bytes, because in practice,
> +		 * some SD cards are slow...
>  		 */
> -		for (i = 2; i < 9; i++) {
> +		for (i = 2; i < 16; i++) {
>  			value = mmc_spi_readbytes(host, 1);
>  			if (value < 0)
>  				goto done;
> 
> ---
> regards
> 
> i. A. Wolfgang Mües
> -- 
> Auerswald GmbH & Co. KG
> Hardware Development
> Telefon: +49 (0)5306 9219 0
> Telefax: +49 (0)5306 9219 94 
> E-Mail: Wolfgang.Mues@...rswald.de
> Web: http://www.auerswald.de
>  
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