linux-kernel - [PATCH] OMAP: Fix for bus width which improves SD card's peformance.

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Date:	Thu, 11 Feb 2010 19:50:23 +0530 (IST)
From:	"kishore kadiyala" <kishore.kadiyala@...com>
To:	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	jarkko.lavinen@...ia.com, madhu.cr@...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@...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

Download attachment "
     "0001-Fix-for-bus-width-which-optimizes-SD-card-s-peforman.patch"" of type "application/octet-stream" (1391 bytes)