[PATCH] wait while adding MMC host to ensure root mounts

[Sergey Yanovich <ynvich@gmail.com>]

MMC hosts are added asynchronously. We need to wait until detect returns to
avoid failed root filesystem mounts.
---8<---
VFS: Cannot open root device "mmcblk0p1" or unknown-block(0,0): error -6
Please append a correct "root=" boot option; here are the available partitions:
mmc0: host does not support reading read-only switch. assuming write-enable.
1f00             256 mtdblock0  (driver?)
1f01             256 mtdblock1  (driver?)
1f02            2560 mtdblock2 mmc0: new SDHC card at address b368
 (driver?)
1f03           29696 mtdblock3  (driver?)
1f04           16384 mtdblock4 mmcblk0: mmc0:b368 USD   3.72 GiB
 (driver?)
 mmcblk0: p1
b300         3910656 mmcblk0  driver: mmcblk
  b301         3906560 mmcblk0p1 00000000-01
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
---8<---

Signed-off-by: Sergey Yanovich <ynvich@gmail.com>
---
 drivers/base/dd.c       |    1 -
 drivers/mmc/core/core.c |    4 +++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 218f1e6..61d3e1b 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -345,7 +345,6 @@ int driver_probe_done(void)
 void wait_for_device_probe(void)
 {
 	/* wait for the known devices to complete their probing */
-
 	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 	async_synchronize_full();
 }
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index aaed768..9790323 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -91,10 +91,11 @@ static int mmc_schedule_delayed_work(struct delayed_work *work,
 /*
  * Internal function. Flush all scheduled work from the MMC work queue.
  */
-static void mmc_flush_scheduled_work(void)
+void mmc_flush_scheduled_work(void)
 {
 	flush_workqueue(workqueue);
 }
+EXPORT_SYMBOL(mmc_flush_scheduled_work);
 
 #ifdef CONFIG_FAIL_MMC_REQUEST
 
@@ -2225,6 +2226,7 @@ void mmc_start_host(struct mmc_host *host)
 	host->rescan_disable = 0;
 	mmc_power_up(host);
 	mmc_detect_change(host, 0);
+	mmc_flush_scheduled_work();
 }
 
 void mmc_stop_host(struct mmc_host *host)
-- 
1.7.10.4