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SubjectRE: [PATCH] OMAP: Fix for bus width which improves SD card's peformance.
Date


> -----Original Message-----
> From: kishore kadiyala [mailto:kishore.kadiyala@ti.com]
> Sent: Thursday, February 11, 2010 8:20 AM
> To: linux-omap@vger.kernel.org; linux-kernel@vger.kernel.org
> Cc: jarkko.lavinen@nokia.com; madhu.cr@ti.com
> Subject: [PATCH] OMAP: Fix for bus width which improves SD card's
> peformance.
>
> 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 peformance.
> This patch fixes the issue and improves the performance of
> SD cards.
>
> Signed-off-by: Kishore Kadiyala <kishore.kadiyala@ti.com>

ACK

Acked-by: Madhusudhan Chikkature <madhu.cr@ti.com>

> ---
> Here are my experiment numbers, on a Class 6 SDHC card:
> Read peformance is increased by 220%
> Write Performance is increased by 52%
>
> drivers/mmc/host/omap_hsmmc.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> index 83f0aff..8c97c22 100644
> --- a/drivers/mmc/host/omap_hsmmc.c
> +++ b/drivers/mmc/host/omap_hsmmc.c
> @@ -2092,7 +2092,7 @@ static int __init omap_hsmmc_probe(struct
> platform_device
> *pdev)
> MMC_CAP_WAIT_WHILE_BUSY;
>
> if (mmc_slot(host).wires >= 8)
> - mmc->caps |= MMC_CAP_8_BIT_DATA;
> + mmc->caps |= (MMC_CAP_8_BIT_DATA | MMC_CAP_4_BIT_DATA);
> else if (mmc_slot(host).wires >= 4)
> mmc->caps |= MMC_CAP_4_BIT_DATA;
>
> --
> 1.6.3.3



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