[PATCH 6/6] ASoC: soc-pcm: fix BE handling of PAUSE_RELEASE

[yixuanjiang <yixuanjiang@google.com>]

From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

[ Upstream commit 3aa1e96a2b95e2ece198f8dd01e96818971b84df ]

A BE connected to more than one FE, e.g. in a mixer case, can go
through the following transitions.

play FE1    -> BE state is START
pause FE1   -> BE state is PAUSED
play FE2    -> BE state is START
stop FE2    -> BE state is STOP (see note [1] below)
release FE1 -> BE state is START
stop FE1    -> BE state is STOP

play FE1    -> BE state is START
pause FE1   -> BE state is PAUSED
play FE2    -> BE state is START
release FE1 -> BE state is START
stop FE2    -> BE state is START
stop FE1    -> BE state is STOP

play FE1    -> BE state is START
play FE2    -> BE state is START (no change)
pause FE1   -> BE state is START (no change)
pause FE2   -> BE state is PAUSED
release FE1 -> BE state is START
release FE2 -> BE state is START (no change)
stop FE1    -> BE state is START (no change)
stop FE2    -> BE state is STOP

The existing code for PAUSE_RELEASE only allows for the case where the
BE is paused, which clearly would not work in the sequences above.

Extend the allowed states to restart the BE when PAUSE_RELEASE is
received, and increase the refcount if the BE is already in START.

[1] the existing logic does not move the BE state back to PAUSED when
the FE2 is stopped. This patch does not change the logic; it would be
painful to keep a history of changes on the FE side, the state machine
is already rather complicated with transitions based on the last BE
state and the trigger type.

Reported-by: Bard Liao <bard.liao@intel.com>
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/20211207173745.15850-7-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Fixes: aa9ff6a4955f ("ASoC: soc-compress: Reposition and add pcm_mutex")
Signed-off-by: Yixuan Jiang <yixuanjiang@google.com>
Cc: stable@vger.kernel.org # 5.15+
---
 sound/soc/soc-pcm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index b6099d36518f5..6e589708b9338 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -2151,7 +2151,10 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			break;
 		case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-			if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
+			if (!be->dpcm[stream].be_start &&
+			    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START) &&
+			    (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++;
-- 
2.40.1.521.gf1e218fcd8-goog