Commit adb24d42 authored Nov 26, 2015 by Wenkai Du Committed by Ulf Hansson Dec 22, 2015

mmc: mmc: Fix incorrect use of driver strength switching HS200 and HS400



Commit cc4f414c ("mmc: mmc: Add driver strength selection")
added driver strength selection for eMMC HS200 and HS400 modes.
That patch also set the driver stength when transitioning through
High Speed mode to HS200/HS400, but driver strength is not defined
for High Speed mode.  While the JEDEC specification is not clear
on this point it has been observed to cause problems for some eMMC,
and removing the driver strength setting in this case makes it
consistent with the normal use of High Speed mode.

Signed-off-by: Wenkai Du <wenkai.du@intel.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

parent 100a606d

drivers/mmc/core/mmc.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -1076,8 +1076,7 @@ static int mmc_select_hs400(struct mmc_card *card)
		mmc_set_clock(host, max_dtr);

		/* Switch card to HS mode */
		val = EXT_CSD_TIMING_HS \|
		card->drive_strength << EXT_CSD_DRV_STR_SHIFT;
		val = EXT_CSD_TIMING_HS;
		err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
		EXT_CSD_HS_TIMING, val,
		card->ext_csd.generic_cmd6_time,
		@@ -1160,8 +1159,7 @@ int mmc_hs400_to_hs200(struct mmc_card *card)
		mmc_set_clock(host, max_dtr);

		/* Switch HS400 to HS DDR */
		val = EXT_CSD_TIMING_HS \|
		card->drive_strength << EXT_CSD_DRV_STR_SHIFT;
		val = EXT_CSD_TIMING_HS;
		err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING,
		val, card->ext_csd.generic_cmd6_time,
		true, send_status, true);

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