mmc: omap: fix for bus width which improves SD card's peformance.
Kishore Kadiyala [Wed, 11 Aug 2010 01:01:46 +0000 (18:01 -0700)]
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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/host/omap_hsmmc.c

index b032828..a0c8515 100644 (file)
@@ -2096,10 +2096,23 @@ static int __init omap_hsmmc_probe(struct platform_device *pdev)
        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;