linux-kernel - [PATCH 6/6] ASoC: soc-pcm: fix BE handling of PAUSE

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Date:   Tue,  7 Dec 2021 11:37:45 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     alsa-devel@...a-project.org
Cc:     tiwai@...e.de, broonie@...nel.org, vkoul@...nel.org,
        Sameer Pujar <spujar@...dia.com>,
        Gyeongtaek Lee <gt82.lee@...sung.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        linux-kernel@...r.kernel.org,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Bard Liao <bard.liao@...el.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Subject: [PATCH 6/6] ASoC: soc-pcm: fix BE handling of PAUSE_RELEASE

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@...el.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@...ux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>
---
 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 05a0f52eb11b..7abfc48b26ca 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -2140,7 +2140,10 @@ 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++;
-- 
2.25.1