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authorAndrew Gabbasov <andrew_gabbasov@mentor.com>2014-12-25 10:22:24 -0600
committerPantelis Antoniou <pantelis.antoniou@konsulko.com>2015-01-19 17:41:52 +0200
commitbf4770731c1fbd23befb1ffcd0436df2262a3199 (patch)
tree835d2d6ac10fa3efb9a52a1af47ba96a33959332 /drivers/mmc
parent9e41a00b572f415bbcc3d8f6fb1c6c541293655b (diff)
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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 <andrew_gabbasov@mentor.com> Tested-by: Alexey Brodkin <abrodkin@synopsys.com> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Diffstat (limited to 'drivers/mmc')
-rw-r--r--drivers/mmc/mmc.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 19ac4c4..bdd7894 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1381,6 +1381,18 @@ static int mmc_startup(struct mmc *mmc)
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
*/