ASoC: soc-pcm: test refcount before triggering

On start/pause_release/resume, when more than one FE is connected to
the same BE, it's possible that the trigger is sent more than
once. This is not desirable, we only want to trigger a BE once, which
is straightforward to implement with a refcount.

For stop/pause/suspend, the problem is more complicated: the check
implemented in snd_soc_dpcm_can_be_free_stop() may fail due to a
conceptual deadlock when we trigger the BE before the FE. In this
case, the FE states have not yet changed, so there are corner cases
where the TRIGGER_STOP is never sent - the dual case of start where
multiple triggers might be sent.

This patch suggests an unconditional trigger in all cases, without
checking the FE states, using a refcount protected by a spinlock.

Signed-off-by: Pierre-Louis Bossart <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Mark Brown <[email protected]>

Author: plbossart

include/sound/soc-dpcm.h

@@ -101,6 +101,8 @@ struct snd_soc_dpcm_runtime {
 	enum snd_soc_dpcm_state state;
 
 	int trigger_pending; /* trigger cmd + 1 if pending, 0 if not */
+
+	int be_start; /* refcount protected by dpcm_lock */
 };
 
 #define for_each_dpcm_fe(be, stream, _dpcm)				\

sound/soc/soc-pcm.c

@@ -1534,7 +1534,7 @@ int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_CLOSE;
 			goto unwind;
 		}
-
+		be->dpcm[stream].be_start = 0;
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_OPEN;
 		count++;
 	}
@@ -2001,6 +2001,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 	int ret = 0;
 	unsigned long flags;
 	enum snd_soc_dpcm_state state;
+	bool do_trigger;
 
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_pcm_substream *be_substream;
@@ -2015,6 +2016,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 		dev_dbg(be->dev, "ASoC: trigger BE %s cmd %d\n",
 			be->dai_link->name, cmd);
 
+		do_trigger = false;
 		switch (cmd) {
 		case SNDRV_PCM_TRIGGER_START:
 			spin_lock_irqsave(&fe->card->dpcm_lock, flags);
@@ -2025,13 +2027,20 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 				continue;
 			}
 			state = be->dpcm[stream].state;
+			if (be->dpcm[stream].be_start == 0)
+				do_trigger = true;
+			be->dpcm[stream].be_start++;
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 
+			if (!do_trigger)
+				continue;
+
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret) {
 				spin_lock_irqsave(&fe->card->dpcm_lock, flags);
 				be->dpcm[stream].state = state;
+				be->dpcm[stream].be_start--;
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				goto end;
 			}
@@ -2045,13 +2054,20 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			}
 
 			state = be->dpcm[stream].state;
+			if (be->dpcm[stream].be_start == 0)
+				do_trigger = true;
+			be->dpcm[stream].be_start++;
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 
+			if (!do_trigger)
+				continue;
+
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret) {
 				spin_lock_irqsave(&fe->card->dpcm_lock, flags);
 				be->dpcm[stream].state = state;
+				be->dpcm[stream].be_start--;
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				goto end;
 			}
@@ -2065,13 +2081,20 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			}
 
 			state = be->dpcm[stream].state;
+			if (be->dpcm[stream].be_start == 0)
+				do_trigger = true;
+			be->dpcm[stream].be_start++;
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 
+			if (!do_trigger)
+				continue;
+
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret) {
 				spin_lock_irqsave(&fe->card->dpcm_lock, flags);
 				be->dpcm[stream].state = state;
+				be->dpcm[stream].be_start--;
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				goto end;
 			}
@@ -2084,9 +2107,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				continue;
 			}
+			if ((be->dpcm[stream].state == SND_SOC_DPCM_STATE_START &&
+			     be->dpcm[stream].be_start == 1) ||
+			    (be->dpcm[stream].state == SND_SOC_DPCM_STATE_PAUSED &&
+			     be->dpcm[stream].be_start == 0))
+				do_trigger = true;
+			be->dpcm[stream].be_start--;
 			spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 
-			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+			if (!do_trigger)
 				continue;
 
 			spin_lock_irqsave(&fe->card->dpcm_lock, flags);
@@ -2098,6 +2127,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			if (ret) {
 				spin_lock_irqsave(&fe->card->dpcm_lock, flags);
 				be->dpcm[stream].state = state;
+				be->dpcm[stream].be_start++;
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				goto end;
 			}
@@ -2109,9 +2139,12 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				continue;
 			}
+			if (be->dpcm[stream].be_start == 1)
+				do_trigger = true;
+			be->dpcm[stream].be_start--;
 			spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 
-			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+			if (!do_trigger)
 				continue;
 
 			spin_lock_irqsave(&fe->card->dpcm_lock, flags);
@@ -2123,6 +2156,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			if (ret) {
 				spin_lock_irqsave(&fe->card->dpcm_lock, flags);
 				be->dpcm[stream].state = state;
+				be->dpcm[stream].be_start++;
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				goto end;
 			}
@@ -2134,9 +2168,12 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				continue;
 			}
+			if (be->dpcm[stream].be_start == 1)
+				do_trigger = true;
+			be->dpcm[stream].be_start--;
 			spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 
-			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+			if (!do_trigger)
 				continue;
 
 			spin_lock_irqsave(&fe->card->dpcm_lock, flags);
@@ -2148,6 +2185,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			if (ret) {
 				spin_lock_irqsave(&fe->card->dpcm_lock, flags);
 				be->dpcm[stream].state = state;
+				be->dpcm[stream].be_start++;
 				spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 				goto end;
 			}