ASoC: SOF: reset DMA state in prepare

When application goes through SUSPEND/STOP->PREPARE->START
cycle, we should always reprogram the SOF device to start
DMA from a known state so that hw_ptr/appl_ptrs remain valid.
This is expected by ALSA core as it resets the buffer
state as part of prepare (see snd_pcm_do_prepare()).

Fix the issue by forcing reconfiguration of the FW with
STREAM_PCM_PARAMS in prepare(). Use combined logic to handle
prepare and the existing flow to reprogram hw-params after
system suspend.

Without the fix, first call to pcm pointer() will return
an invalid hw_ptr and application may immediately observe XRUN
status, unless "start_threshold" SW parameter is set to maximum
value by the application.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>

sound/soc/sof/pcm.c

@@ -208,12 +208,11 @@ static int sof_pcm_hw_params(struct snd_pcm_substream *substream,
 	if (ret < 0)
 		return ret;
 
+	spcm->prepared[substream->stream] = true;
+
 	/* save pcm hw_params */
 	memcpy(&spcm->params[substream->stream], params, sizeof(*params));
 
-	/* clear hw_params_upon_resume flag */
-	spcm->hw_params_upon_resume[substream->stream] = 0;
-
 	return ret;
 }
 
@@ -236,6 +235,9 @@ static int sof_pcm_hw_free(struct snd_pcm_substream *substream)
 	if (!spcm)
 		return -EINVAL;
 
+	if (!spcm->prepared[substream->stream])
+		return 0;
+
 	dev_dbg(sdev->dev, "pcm: free stream %d dir %d\n", spcm->pcm.pcm_id,
 		substream->stream);
 
@@ -258,6 +260,8 @@ static int sof_pcm_hw_free(struct snd_pcm_substream *substream)
 	if (ret < 0)
 		dev_err(sdev->dev, "error: platform hw free failed\n");
 
+	spcm->prepared[substream->stream] = false;
+
 	return ret;
 }
 
@@ -278,11 +282,7 @@ static int sof_pcm_prepare(struct snd_pcm_substream *substream)
 	if (!spcm)
 		return -EINVAL;
 
-	/*
+	if (spcm->prepared[substream->stream])
-	 * check if hw_params needs to be set-up again.
-	 * This is only needed when resuming from system sleep.
-	 */
-	if (!spcm->hw_params_upon_resume[substream->stream])
 		return 0;
 
 	dev_dbg(sdev->dev, "pcm: prepare stream %d dir %d\n", spcm->pcm.pcm_id,
@@ -311,6 +311,7 @@ static int sof_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 	struct snd_sof_pcm *spcm;
 	struct sof_ipc_stream stream;
 	struct sof_ipc_reply reply;
+	bool reset_hw_params = false;
 	int ret;
 
 	/* nothing to do for BE */
@@ -351,6 +352,7 @@ static int sof_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
 		stream.hdr.cmd |= SOF_IPC_STREAM_TRIG_STOP;
+		reset_hw_params = true;
 		break;
 	default:
 		dev_err(sdev->dev, "error: unhandled trigger cmd %d\n", cmd);
@@ -363,17 +365,17 @@ static int sof_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 	ret = sof_ipc_tx_message(sdev->ipc, stream.hdr.cmd, &stream,
 				 sizeof(stream), &reply, sizeof(reply));
 
-	if (ret < 0 || cmd != SNDRV_PCM_TRIGGER_SUSPEND)
+	if (ret < 0 || !reset_hw_params)
 		return ret;
 
 	/*
-	 * The hw_free op is usually called when the pcm stream is closed.
+	 * In case of stream is stopped, DSP must be reprogrammed upon
-	 * Since the stream is not closed during suspend, the DSP needs to be
+	 * restart, so free PCM here.
-	 * notified explicitly to free pcm to prevent errors upon resume.
 	 */
 	stream.hdr.size = sizeof(stream);
 	stream.hdr.cmd = SOF_IPC_GLB_STREAM_MSG | SOF_IPC_STREAM_PCM_FREE;
 	stream.comp_id = spcm->stream[substream->stream].comp_id;
+	spcm->prepared[substream->stream] = false;
 
 	/* send IPC to the DSP */
 	return sof_ipc_tx_message(sdev->ipc, stream.hdr.cmd, &stream,
@@ -481,6 +483,7 @@ static int sof_pcm_open(struct snd_pcm_substream *substream)
 	spcm->stream[substream->stream].posn.host_posn = 0;
 	spcm->stream[substream->stream].posn.dai_posn = 0;
 	spcm->stream[substream->stream].substream = substream;
+	spcm->prepared[substream->stream] = false;
 
 	ret = snd_sof_pcm_platform_open(sdev, substream);
 	if (ret < 0)

sound/soc/sof/pm.c

@@ -233,7 +233,7 @@ static int sof_set_hw_params_upon_resume(struct snd_sof_dev *sdev)
 
 			state = substream->runtime->status->state;
 			if (state == SNDRV_PCM_STATE_SUSPENDED)
-				spcm->hw_params_upon_resume[dir] = 1;
+				spcm->prepared[dir] = false;
 		}
 	}
 

sound/soc/sof/sof-priv.h

@@ -295,7 +295,7 @@ struct snd_sof_pcm {
 	struct snd_sof_pcm_stream stream[2];
 	struct list_head list;	/* list in sdev pcm list */
 	struct snd_pcm_hw_params params[2];
-	int hw_params_upon_resume[2]; /* set up hw_params upon resume */
+	bool prepared[2]; /* PCM_PARAMS set successfully */
 };
 
 /* ALSA SOF Kcontrol device */