mmc: support unsafe resume of cards

Since many have the system root on MMC/SD we must allow some foot
shooting when it comes to resume.

We cannot detect if a card is removed and reinserted during suspend,
so the safe approach would be to assume it was, avoiding potential
filesystem corruption. This will of course not work if you cannot
release the card before suspend.

This commit adds a compile time option that makes the MMC layer
assume the card wasn't touched if it is redetected upon resume.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

1 files changed, 23 insertions, 6 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 75333a2461df..72c7cf4a9f9d 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -677,14 +677,19 @@ int mmc_suspend_host(struct mmc_host *host, pm_message_t state)
 
         mmc_bus_get(host);
         if (host->bus_ops && !host->bus_dead) {
-                if (host->bus_ops->remove)
-                        host->bus_ops->remove(host);
-                mmc_detach_bus(host);
+                if (host->bus_ops->suspend)
+                        host->bus_ops->suspend(host);
+                if (!host->bus_ops->resume) {
+                        if (host->bus_ops->remove)
+                                host->bus_ops->remove(host);
+
+                        mmc_claim_host(host);
+                        mmc_detach_bus(host);
+                        mmc_release_host(host);
+                }
         }
         mmc_bus_put(host);
 
-        BUG_ON(host->card);
-
         mmc_power_off(host);
 
         return 0;
@@ -698,7 +703,19 @@ EXPORT_SYMBOL(mmc_suspend_host);
  */
 int mmc_resume_host(struct mmc_host *host)
 {
-        mmc_rescan(&host->detect.work);
+        mmc_bus_get(host);
+        if (host->bus_ops && !host->bus_dead) {
+                mmc_power_up(host);
+                BUG_ON(!host->bus_ops->resume);
+                host->bus_ops->resume(host);
+        }
+        mmc_bus_put(host);
+
+        /*
+         * We add a slight delay here so that resume can progress
+         * in parallel.
+         */
+        mmc_detect_change(host, 1);
 
         return 0;
 }