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 the BE PCM
stream lock.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20211207173745.15850-6-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/include/sound/soc-dpcm.h b/include/sound/soc-dpcm.h
index bc7af90..75b92d8 100644 (file)
--- a/include/sound/soc-dpcm.h
+++ b/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 BE stream pcm lock */
 };
 
 #define for_each_dpcm_fe(be, stream, _dpcm)                            \

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 7043857..05a0f52 100644 (file)
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1619,7 +1619,7 @@ 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++;
        }
@@ -2105,14 +2105,21 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 
                switch (cmd) {
                case SNDRV_PCM_TRIGGER_START:
-                       if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_PREPARE) &&
+                       if (!be->dpcm[stream].be_start &&
+                           (be->dpcm[stream].state != SND_SOC_DPCM_STATE_PREPARE) &&
                            (be->dpcm[stream].state != SND_SOC_DPCM_STATE_STOP) &&
                            (be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
                                goto next;
 
+                       be->dpcm[stream].be_start++;
+                       if (be->dpcm[stream].be_start != 1)
+                               goto next;
+
                        ret = soc_pcm_trigger(be_substream, cmd);
-                       if (ret)
+                       if (ret) {
+                               be->dpcm[stream].be_start--;
                                goto next;
+                       }
 
                        be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
                        break;
@@ -2120,9 +2127,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
                        if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_SUSPEND))
                                goto next;
 
+                       be->dpcm[stream].be_start++;
+                       if (be->dpcm[stream].be_start != 1)
+                               goto next;
+
                        ret = soc_pcm_trigger(be_substream, cmd);
-                       if (ret)
+                       if (ret) {
+                               be->dpcm[stream].be_start--;
                                goto next;
+                       }
 
                        be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
                        break;
@@ -2130,9 +2143,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
                        if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
                                goto next;
 
+                       be->dpcm[stream].be_start++;
+                       if (be->dpcm[stream].be_start != 1)
+                               goto next;
+
                        ret = soc_pcm_trigger(be_substream, cmd);
-                       if (ret)
+                       if (ret) {
+                               be->dpcm[stream].be_start--;
                                goto next;
+                       }
 
                        be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
                        break;
@@ -2141,12 +2160,18 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
                            (be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
                                goto next;
 
-                       if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+                       if (be->dpcm[stream].state == SND_SOC_DPCM_STATE_START)
+                               be->dpcm[stream].be_start--;
+
+                       if (be->dpcm[stream].be_start != 0)
                                goto next;
 
                        ret = soc_pcm_trigger(be_substream, cmd);
-                       if (ret)
+                       if (ret) {
+                               if (be->dpcm[stream].state == SND_SOC_DPCM_STATE_START)
+                                       be->dpcm[stream].be_start++;
                                goto next;
+                       }
 
                        be->dpcm[stream].state = SND_SOC_DPCM_STATE_STOP;
                        break;
@@ -2154,12 +2179,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
                        if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START)
                                goto next;
 
-                       if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+                       be->dpcm[stream].be_start--;
+                       if (be->dpcm[stream].be_start != 0)
                                goto next;
 
                        ret = soc_pcm_trigger(be_substream, cmd);
-                       if (ret)
+                       if (ret) {
+                               be->dpcm[stream].be_start++;
                                goto next;
+                       }
 
                        be->dpcm[stream].state = SND_SOC_DPCM_STATE_SUSPEND;
                        break;
@@ -2167,12 +2195,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
                        if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START)
                                goto next;
 
-                       if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+                       be->dpcm[stream].be_start--;
+                       if (be->dpcm[stream].be_start != 0)
                                goto next;
 
                        ret = soc_pcm_trigger(be_substream, cmd);
-                       if (ret)
+                       if (ret) {
+                               be->dpcm[stream].be_start++;
                                goto next;
+                       }
 
                        be->dpcm[stream].state = SND_SOC_DPCM_STATE_PAUSED;
                        break;