mmc: sdio: avoid spurious calls to interrupt handlers

Commit 06e8935feb ("optimized SDIO IRQ handling for single irq")
introduced some spurious calls to SDIO function interrupt handlers,
such as when the SDIO IRQ thread is started, or the safety check
performed upon a system resume. Let's add a flag to perform the
optimization only when a real interrupt is signaled by the host
driver and we know there is no point confirming it.

Reported-by: Sujit Reddy Thumma <[e-mail]>
Signed-off-by: Nicolas Pitre <[e-mail]>
Cc: stable <[e-mail]>
Signed-off-by: Chris Ball <[e-mail]>

drivers/mmc/core/sdio.c

···
 	}
 
 	if (!err && host->sdio_irqs)
-		mmc_signal_sdio_irq(host);
+		wake_up_process(host->sdio_irq_thread);
 	mmc_release_host(host);
 
 	/*

drivers/mmc/core/sdio_irq.c

···
 
 #include "sdio_ops.h"
 
-static int process_sdio_pending_irqs(struct mmc_card *card)
+static int process_sdio_pending_irqs(struct mmc_host *host)
 {
+	struct mmc_card *card = host->card;
 	int i, ret, count;
 	unsigned char pending;
 	struct sdio_func *func;
 
 	/*
 	 * Optimization, if there is only 1 function interrupt registered
-	 * call irq handler directly
+	 * and we know an IRQ was signaled then call irq handler directly.
+	 * Otherwise do the full probe.
 	 */
 	func = card->sdio_single_irq;
-	if (func) {
+	if (func && host->sdio_irq_pending) {
 		func->irq_handler(func);
 		return 1;
 	}
···
 		ret = __mmc_claim_host(host, &host->sdio_irq_thread_abort);
 		if (ret)
 			break;
-		ret = process_sdio_pending_irqs(host->card);
+		ret = process_sdio_pending_irqs(host);
+		host->sdio_irq_pending = false;
 		mmc_release_host(host);
 
 		/*

include/linux/mmc/host.h

···
 
 	unsigned int		sdio_irqs;
 	struct task_struct	*sdio_irq_thread;
+	bool			sdio_irq_pending;
 	atomic_t		sdio_irq_thread_abort;
 
 	mmc_pm_flag_t		pm_flags;	/* requested pm features */
···
 static inline void mmc_signal_sdio_irq(struct mmc_host *host)
 {
 	host->ops->enable_sdio_irq(host, 0);
+	host->sdio_irq_pending = true;
 	wake_up_process(host->sdio_irq_thread);
 }