ALSA: pcm: Add card sync_irq field

Many PCI and other drivers performs snd_pcm_period_elapsed() simply in
its interrupt handler, so the sync_stop operation is just to call
synchronize_irq().  Instead of putting this call multiple times,
introduce the common card->sync_irq field.  When this field is set,
PCM core performs synchronize_irq() for sync-stop operation.  Each
driver just needs to copy its local IRQ number to card->sync_irq, and
that's all we need.

Link: https://lore.kernel.org/r/20191117085308.23915-8-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/core.h

@@ -117,6 +117,7 @@ struct snd_card {
 	struct device card_dev;		/* cardX object for sysfs */
 	const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */
 	bool registered;		/* card_dev is registered? */
+	int sync_irq;			/* assigned irq, used for PCM sync */
 	wait_queue_head_t remove_sleep;
 
 #ifdef CONFIG_PM

sound/core/init.c

@@ -215,6 +215,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
 	init_waitqueue_head(&card->power_sleep);
 #endif
 	init_waitqueue_head(&card->remove_sleep);
+	card->sync_irq = -1;
 
 	device_initialize(&card->card_dev);
 	card->card_dev.parent = parent;

sound/core/pcm_native.c

@@ -574,6 +574,8 @@ static void snd_pcm_sync_stop(struct snd_pcm_substream *substream)
 		substream->runtime->stop_operating = false;
 		if (substream->ops->sync_stop)
 			substream->ops->sync_stop(substream);
+		else if (substream->pcm->card->sync_irq > 0)
+			synchronize_irq(substream->pcm->card->sync_irq);
 	}
 }