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From: Jarkko Nikula on 31 Mar 2010 09:20
On Wed, 31 Mar 2010 12:33:01 +0530
kishore kadiyala <kishorek.kadiyala(a)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(a)ti.com>
> Signed-off-by: Venkatraman S <svenkatr(a)ti.com>
> Acked-by: Madhusudhan Chikkature <madhu.cr(a)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(a)gmail.com>
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