[4.2.y-ckt stable] Patch "mmc: mmc: Fix incorrect use of driver strength switching HS200 and HS400" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt3.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From d4bdd1a311e2af9fc873071269b9978d721bf4f6 Mon Sep 17 00:00:00 2001
From: Wenkai Du <wenkai.du at intel.com>
Date: Thu, 26 Nov 2015 14:00:44 +0200
Subject: mmc: mmc: Fix incorrect use of driver strength switching HS200 and
 HS400

commit adb24d42a516bca8b9741ed21206509daaab5b13 upstream.

Commit cc4f414c885c ("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 at intel.com>
Signed-off-by: Adrian Hunter <adrian.hunter at intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/mmc/core/mmc.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 748eddf..c3c48b1 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -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);
--
1.9.1