mmc: skip detection of nonremovable cards on rescan

mmc_rescan() checks whether registered cards are still present before
skipping them, by calling the bus-specific ->detect() handler.

With buses that support runtime PM, the card may be powered off at
this point, so they need to be powered on and fully reinitialized before
->detect() executes.

This whole process is redundant with nonremovable cards; in those cases,
we can safely skip calling ->detect() and implicitly assume its success.
Signed-off-by: NOhad Ben-Cohen <ohad@wizery.com>
Reviewed-by: NChris Ball <cjb@laptop.org>
Signed-off-by: NChris Ball <cjb@laptop.org>

drivers/mmc/core/core.c

@@ -1506,8 +1506,12 @@ void mmc_rescan(struct work_struct *work)
 
 	mmc_bus_get(host);
 
-	/* if there is a card registered, check whether it is still present */
-	if ((host->bus_ops != NULL) && host->bus_ops->detect && !host->bus_dead)
+	/*
+	 * if there is a _removable_ card registered, check whether it is
+	 * still present
+	 */
+	if (host->bus_ops && host->bus_ops->detect && !host->bus_dead
+	    && mmc_card_is_removable(host))
 		host->bus_ops->detect(host);
 
 	mmc_bus_put(host);