[PATCH] ALSA: pcm: Optimize cpu_latency_qos_*() calls

[Takashi Iwai]

We have a few cpu_latency_qos_*() calls in PCM callbacks, but they
seem suboptimal in a few aspects:
- We call them at each time when the hw_params changed, but explicitly
  do remove and (re-)add; this could be
  cpu_latency_qos_update_request(), instead
- The setup of cpu_latency_qos_*() doesn't have to be in hw_params at
  all; it's not the place where the actual parameters are set up, but
  rather better at the prepare callback.
- The hw_free calls cpu_latency_qos_remove_request() unconditionally,
  which may be poking a WARNING when it wasn't queued.

For addressing the issues above, this patch cleans up and reorganize
the cpu_latency_qos_*() calls in the PCM core by a couple helper
functions.  Now, they are set up at prepare callback, and cleared at
hw_free and release callbacks via the new helpers.

Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
 sound/core/pcm_native.c | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 5abe16a03b34..6efaebc7f8b4 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -778,11 +778,32 @@ EXPORT_SYMBOL_GPL(snd_pcm_runtime_buffer_set_silence);
 #define is_oss_stream(substream)	false
 #endif
 
+static void pcm_qos_req_clear(struct snd_pcm_substream *substream)
+{
+	if (cpu_latency_qos_request_active(&substream->latency_pm_qos_req))
+		cpu_latency_qos_remove_request(&substream->latency_pm_qos_req);
+}
+
+static void pcm_qos_req_update(struct snd_pcm_substream *substream, int usecs)
+{
+	if (usecs < 0) {
+		pcm_qos_req_clear(substream);
+		return;
+	}
+
+	if (cpu_latency_qos_request_active(&substream->latency_pm_qos_req))
+		cpu_latency_qos_update_request(&substream->latency_pm_qos_req,
+					       usecs);
+	else
+		cpu_latency_qos_add_request(&substream->latency_pm_qos_req,
+					    usecs);
+}
+
 static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
 			     struct snd_pcm_hw_params *params)
 {
 	struct snd_pcm_runtime *runtime;
-	int err, usecs;
+	int err;
 	unsigned int bits;
 	snd_pcm_uframes_t frames;
 
@@ -889,12 +910,6 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
 	snd_pcm_timer_resolution_change(substream);
 	snd_pcm_set_state(substream, SNDRV_PCM_STATE_SETUP);
 
-	if (cpu_latency_qos_request_active(&substream->latency_pm_qos_req))
-		cpu_latency_qos_remove_request(&substream->latency_pm_qos_req);
-	usecs = period_to_usecs(runtime);
-	if (usecs >= 0)
-		cpu_latency_qos_add_request(&substream->latency_pm_qos_req,
-					    usecs);
 	err = 0;
  _error:
 	if (err) {
@@ -971,7 +986,7 @@ static int snd_pcm_hw_free(struct snd_pcm_substream *substream)
 		goto unlock;
 	result = do_hw_free(substream);
 	snd_pcm_set_state(substream, SNDRV_PCM_STATE_OPEN);
-	cpu_latency_qos_remove_request(&substream->latency_pm_qos_req);
+	pcm_qos_req_clear(substream);
  unlock:
 	snd_pcm_buffer_access_unlock(runtime);
 	return result;
@@ -2005,6 +2020,7 @@ static int snd_pcm_do_prepare(struct snd_pcm_substream *substream,
 	err = substream->ops->prepare(substream);
 	if (err < 0)
 		return err;
+	pcm_qos_req_update(substream, period_to_usecs(substream->runtime));
 	return snd_pcm_do_reset(substream, state);
 }
 
@@ -2795,8 +2811,7 @@ void snd_pcm_release_substream(struct snd_pcm_substream *substream)
 		substream->ops->close(substream);
 		substream->hw_opened = 0;
 	}
-	if (cpu_latency_qos_request_active(&substream->latency_pm_qos_req))
-		cpu_latency_qos_remove_request(&substream->latency_pm_qos_req);
+	pcm_qos_req_clear(substream);
 	if (substream->pcm_release) {
 		substream->pcm_release(substream);
 		substream->pcm_release = NULL;
-- 
2.55.0