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Date: Wed, 31 Mar 2010 16:11:53 +0300
From: Jarkko Nikula <jhnikula@gmail.com>
To: kishore kadiyala <kishorek.kadiyala@gmail.com>
Cc: Vimal Singh <vimal.newwork@gmail.com>, Madhusudhan <madhu.cr@ti.com>,
       tony@atomide.com, svenkatr@ti.com, linux-omap@vger.kernel.org,
       linux-kernel@vger.kernel.org, jarkko.lavinen@nokia.com
Subject: Re: [PATCH-V2] OMAP: Fix for bus width which improves SD card's 
 peformance.
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On Wed, 31 Mar 2010 12:33:01 +0530
kishore kadiyala <kishorek.kadiyala@gmail.com> wrote:

> This patch improves low speeds for SD cards.
> OMAP-MMC controller's can support maximum bus width of '8'.
> when bus width is mentioned as "8" in controller data,the SD
> stack will check whether bus width is "4" and if not it will
> set bus width to "1" and there by degrading performance.
> This patch fixes the issue and improves the performance of
> SD cards.
> 
> Signed-off-by: Kishore Kadiyala <kishore.kadiyala@ti.com>
> Signed-off-by: Venkatraman S <svenkatr@ti.com>
> Acked-by: Madhusudhan Chikkature <madhu.cr@ti.com>
> 
> ---
> In V2 : Appended Signed-off by Venkat and Ack by Madhu
> 
>  Here are my experiment numbers, on a Class 6 SDHC card:
>  Read peformance is increased by 220%
>  Write Performance is increased by 52%
> 
Some results from the BeagleBoard and 2 GB SD card:

sync; time (dd if=/dev/zero of=`date +%s`.bin bs=1M count=100; sync)
-> ~40 % improvement over 4 writes.

time dd if=12700xxxxx.bin of=/dev/null
-> ~96 % improvement over 4 reads.

Feel free to add my tested-by.

Tested-by: Jarkko Nikula <jhnikula@gmail.com>