mmc: Delay the card_event callback into the mmc_rescan worker

This change removes the callback from atomic context which it doesn't
need to be in, and puts it in line with the debounced rescan.

This code is based on these e-mail threads with Christian Daudt:

  https://lkml.org/lkml/2013/8/19/539
  https://lkml.org/lkml/2014/3/19/79

Signed-off-by: Markus Mayer <markus.mayer@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>

drivers/mmc/core/core.c

@@ -2403,6 +2403,11 @@ void mmc_rescan(struct work_struct *work)
 		container_of(work, struct mmc_host, detect.work);
 	int i;
 
+	if (host->trigger_card_event && host->ops->card_event) {
+		host->ops->card_event(host);
+		host->trigger_card_event = false;
+	}
+
 	if (host->rescan_disable)
 		return;
 

drivers/mmc/core/slot-gpio.c

@@ -32,9 +32,7 @@ static irqreturn_t mmc_gpio_cd_irqt(int irq, void *dev_id)
 	/* Schedule a card detection after a debounce timeout */
 	struct mmc_host *host = dev_id;
 
-	if (host->ops->card_event)
-		host->ops->card_event(host);
-
+	host->trigger_card_event = true;
 	mmc_detect_change(host, msecs_to_jiffies(200));
 
 	return IRQ_HANDLED;