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@xxxxxx> Signed-off-by: Venkatraman S <svenkatr@xxxxxx> Signed-off-by: Nishanth Menon <nm@xxxxxx> Acked-by: Madhusudhan Chikkature <madhu.cr@xxxxxx> Tested-by: Jarkko Nikula <jhnikula@xxxxxxxxx> --- In V5 : Rebasing on 2.6.35-rc3 In V4 : Updated with Nishanth's comments and appened his Signed-off http://marc.info/?t=127169149300006&r=1&w=2 In V3 : Updated with Madhu's comments and appended Tested by Nikula 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% drivers/mmc/host/omap_hsmmc.c | 17 +++++++++++++++-- 1 files changed, 15 insertions(+), 2 deletions(-) diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c index b032828..a0c8515 100644 --- a/drivers/mmc/host/omap_hsmmc.c +++ b/drivers/mmc/host/omap_hsmmc.c @@ -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; -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
