Patch "mmc: mmc: Fix partition switch timeout for some eMMCs" has been added to the 4.6-stable tree

This is a note to let you know that I've just added the patch titled

mmc: mmc: Fix partition switch timeout for some eMMCs

to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mmc-mmc-fix-partition-switch-timeout-for-some-emmcs.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Adrian Hunter <[email protected]>
Date: Thu, 5 May 2016 08:12:28 +0300
Subject: mmc: mmc: Fix partition switch timeout for some eMMCs

From: Adrian Hunter <[email protected]>

commit 1c447116d017a98c90f8f71c8c5a611e0aa42178 upstream.

Some eMMCs set the partition switch timeout too low.

Now typically eMMCs are considered a critical component (e.g. because they store the root file system) and consequently are expected to be reliable. Thus we can neglect the use case where eMMCs can't switch reliably and we might want a lower timeout to facilitate speedy recovery.

Although we could employ a quirk for the cards that are affected (if we could identify them all), as described above, there is little benefit to having a low timeout, so instead simply set a minimum timeout.

The minimum is set to 300ms somewhat arbitrarily - the examples that have been seen had a timeout of 10ms but were sometimes taking 60-70ms.

---
 drivers/mmc/core/mmc.c |    7 +++++++
 1 file changed, 7 insertions(+)

@@ -333,6 +333,9 @@ static void mmc_manage_gp_partitions(str
 	}
 }
 
+/* Minimum partition switch timeout in milliseconds */
+#define MMC_MIN_PART_SWITCH_TIME	300
+
 /*
  * Decode extended CSD.
  */

@@ -397,6 +400,10 @@ static int mmc_decode_ext_csd(struct mmc
 
 		/* EXT_CSD value is in units of 10ms, but we store in ms */
 		card->ext_csd.part_time = 10 * ext_csd[EXT_CSD_PART_SWITCH_TIME];
+		/* Some eMMC set the value too low so set a minimum */
+		if (card->ext_csd.part_time &&
+		    card->ext_csd.part_time < MMC_MIN_PART_SWITCH_TIME)
+			card->ext_csd.part_time = MMC_MIN_PART_SWITCH_TIME;
 
 		/* Sleep / awake timeout in 100ns units */
 		if (sa_shift > 0 && sa_shift <= 0x17)

Patches currently in stable-queue which might be from [email protected] are

queue-4.6/mmc-sdhci-acpi-ensure-connected-devices-are-powered-when-probing.patch queue-4.6/mmc-mmc-fix-partition-switch-timeout-for-some-emmcs.patch queue-4.6/mmc-longer-timeout-for-long-read-time-quirk.patch queue-4.6/mmc-sdhci-acpi-remove-mmc_cap_bus_width_test-for-intel-controllers.patch queue-4.6/mmc-sdhci-pci-remove-mmc_cap_bus_width_test-for-intel-controllers.patch