[alsa-devel] [PATCH 1/2] ALSA: hda: Use waitqueue for RIRB in HDA-core helper, too

[Takashi Iwai <tiwai@suse.de>]

This patch implements the same logic that was done for the legacy
HD-audio controller driver by the commit 88452da92ba2 ("ALSA: hda: Use
standard waitqueue for RIRB wakeup") to the HDA-core helper code,
too.  This makes snd_hdac_bus_get_response() waiting for the response
with bus->rirb_wq instead of polling when bus->polling is false.
It'll save both CPU time and response latency.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/hda/hdac_controller.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/sound/hda/hdac_controller.c b/sound/hda/hdac_controller.c
index cd1c3b282657..61950b83b8c9 100644
--- a/sound/hda/hdac_controller.c
+++ b/sound/hda/hdac_controller.c
@@ -241,30 +241,42 @@ int snd_hdac_bus_get_response(struct hdac_bus *bus, unsigned int addr,
 {
 	unsigned long timeout;
 	unsigned long loopcounter;
+	wait_queue_entry_t wait;
 
+	init_wait_entry(&wait, 0);
 	timeout = jiffies + msecs_to_jiffies(1000);
 
 	for (loopcounter = 0;; loopcounter++) {
 		spin_lock_irq(&bus->reg_lock);
+		if (!bus->polling_mode)
+			prepare_to_wait(&bus->rirb_wq, &wait,
+					TASK_UNINTERRUPTIBLE);
 		if (bus->polling_mode)
 			snd_hdac_bus_update_rirb(bus);
 		if (!bus->rirb.cmds[addr]) {
 			if (res)
 				*res = bus->rirb.res[addr]; /* the last value */
+			if (!bus->polling_mode)
+				finish_wait(&bus->rirb_wq, &wait);
 			spin_unlock_irq(&bus->reg_lock);
 			return 0;
 		}
 		spin_unlock_irq(&bus->reg_lock);
 		if (time_after(jiffies, timeout))
 			break;
-		if (loopcounter > 3000)
+		if (!bus->polling_mode) {
+			schedule_timeout(msecs_to_jiffies(2));
+		} else if (loopcounter > 3000) {
 			msleep(2); /* temporary workaround */
-		else {
+		} else {
 			udelay(10);
 			cond_resched();
 		}
 	}
 
+	if (!bus->polling_mode)
+		finish_wait(&bus->rirb_wq, &wait);
+
 	return -EIO;
 }
 EXPORT_SYMBOL_GPL(snd_hdac_bus_get_response);
-- 
2.16.4

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