[patch 040/177] mmc: omap: fix for bus width which improves SD card's peformance.

[patch 040/177] mmc: omap: fix for bus width which improves SD card's peformance.

[akpm]

From: Kishore Kadiyala <kishore.kadiyala@ti.com>

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>
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Madhusudhan Chikkature <madhu.cr@ti.com>
Tested-by: Jarkko Nikula <jhnikula@gmail.com>
Cc: Adrian Hunter <adrian.hunter@nokia.com>
Cc: Matt Fleming <matt@console-pimps.org>
Cc: Tony Lindgren <tony@atomide.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/mmc/host/omap_hsmmc.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff -puN drivers/mmc/host/omap_hsmmc.c~mmc-omap-fix-for-bus-width-which-improves-sd-cards-peformance drivers/mmc/host/omap_hsmmc.c
--- a/drivers/mmc/host/omap_hsmmc.c~mmc-omap-fix-for-bus-width-which-improves-sd-cards-peformance
+++ a/drivers/mmc/host/omap_hsmmc.c
@@ -2096,10 +2096,23 @@ static int __init omap_hsmmc_probe(struc
 	mmc->caps |= MMC_CAP_MMC_HIGHSPEED | MMC_CAP_SD_HIGHSPEED |
 		     MMC_CAP_WAIT_WHILE_BUSY;
 
-	if (mmc_slot(host).wires >= 8)
+	switch (mmc_slot(host).wires) {
+	case 8:
 		mmc->caps |= MMC_CAP_8_BIT_DATA;
-	else if (mmc_slot(host).wires >= 4)
+		/* Fall through */
+	case 4:
 		mmc->caps |= MMC_CAP_4_BIT_DATA;
+		break;
+	case 1:
+		/* Nothing to crib here */
+	case 0:
+		/* Assuming nothing was given by board, Core use's 1-Bit */
+		break;
+	default:
+		/* Completely unexpected.. Core goes with 1-Bit Width */
+		dev_crit(mmc_dev(host->mmc), "Invalid width %d\n used!"
+			"using 1 instead\n", mmc_slot(host).wires);
+	}
 
 	if (mmc_slot(host).nonremovable)
 		mmc->caps |= MMC_CAP_NONREMOVABLE;
_