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ASoC: soc-pcm: test refcount before triggering
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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 <pierre-louis.bossart@linux.intel.com>
Message-Id: <20210817164054.250028-3-pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
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@plbossart @broonie
plbossart authored and broonie committed Aug 26, 2021
1 parent 0c75fc7 commit 6479f75
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Showing 2 changed files with 44 additions and 4 deletions.
2 changes: 2 additions & 0 deletions include/sound/soc-dpcm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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) \
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46 changes: 42 additions & 4 deletions sound/soc/soc-pcm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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++;
}
Expand Down Expand Up @@ -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;
Expand All @@ -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);
Expand All @@ -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;
}
Expand All @@ -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;
}
Expand All @@ -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;
}
Expand All @@ -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);
Expand All @@ -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;
}
Expand All @@ -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);
Expand All @@ -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;
}
Expand All @@ -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);
Expand All @@ -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;
}
Expand Down

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