From bf4770731c1fbd23befb1ffcd0436df2262a3199 Mon Sep 17 00:00:00 2001 From: Andrew Gabbasov Date: Thu, 25 Dec 2014 10:22:24 -0600 Subject: mmc: Avoid redundant switching to 1-bit bus width for MMC cards If all the commands switching an MMC card to 4- or 8-bit bus width fail, and the bus width for the controller and the driver is still set to default 1 bit, there is no need to send one more command to switch the card to 1-bit bus width. Also, if the card or host controller do not support wider bus widths, there is no need to send a switch command at all. However, if one of switch commands succeeds, but the subsequent ext_csd fields comparison fails, the card should be switched to some other bus width (next in the list for the loop), or to default 1-bit bus width as a last resort. That's why it would be incorrect to just remove the 1-bit bus width case from the list, it should still be processed in some cases. panto: Minor cosmetic edit removing superfluous parentheses. Signed-off-by: Andrew Gabbasov Tested-by: Alexey Brodkin Signed-off-by: Pantelis Antoniou --- drivers/mmc/mmc.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'drivers/mmc/mmc.c') diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c index 19ac4c482f..bdd7894231 100644 --- a/drivers/mmc/mmc.c +++ b/drivers/mmc/mmc.c @@ -1380,6 +1380,18 @@ static int mmc_startup(struct mmc *mmc) unsigned int extw = ext_csd_bits[idx]; unsigned int caps = ext_to_hostcaps[extw]; + /* + * If the bus width is still not changed, + * don't try to set the default again. + * Otherwise, recover from switch attempts + * by switching to 1-bit bus width. + */ + if (extw == EXT_CSD_BUS_WIDTH_1 && + mmc->bus_width == 1) { + err = 0; + break; + } + /* * Check to make sure the card and controller support * these capabilities -- cgit