linux-kernel - [PATCH v2 1/5] ASoC: q6apm-dai: schedule all available frames to avoid dsp under-runs

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Message-Id: <20250220162847.11994-2-srinivas.kandagatla@linaro.org>
Date: Thu, 20 Feb 2025 16:28:43 +0000
From: srinivas.kandagatla@...aro.org
To: broonie@...nel.org
Cc: perex@...ex.cz,
	tiwai@...e.com,
	krzysztof.kozlowski@...aro.org,
	linux-sound@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	dmitry.baryshkov@...aro.org,
	johan+linaro@...nel.org,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: [PATCH v2 1/5] ASoC: q6apm-dai: schedule all available frames to avoid dsp under-runs

From: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>

With the existing code, we are only setting up one period at a time, in a
ping-pong buffer style. This triggers lot of underruns in the dsp
leading to jitter noise during audio playback.

Fix this by scheduling all available periods, this will ensure that the dsp
has enough buffer feed and ultimatley fixing the underruns and audio
distortion.

Fixes: 9b4fe0f1cd79 ("ASoC: qdsp6: audioreach: add q6apm-dai support")
Reported-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
---
 sound/soc/qcom/qdsp6/q6apm-dai.c | 33 +++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/sound/soc/qcom/qdsp6/q6apm-dai.c b/sound/soc/qcom/qdsp6/q6apm-dai.c
index c9404b5934c7..eba51e88a297 100644
--- a/sound/soc/qcom/qdsp6/q6apm-dai.c
+++ b/sound/soc/qcom/qdsp6/q6apm-dai.c
@@ -70,6 +70,7 @@ struct q6apm_dai_rtd {
 	unsigned int bytes_received;
 	unsigned int copied_total;
 	uint16_t bits_per_sample;
+	unsigned int pb_tail;
 	bool next_track;
 	enum stream_state state;
 	struct q6apm_graph *graph;
@@ -134,8 +135,6 @@ static void event_handler(uint32_t opcode, uint32_t token, void *payload, void *
 		prtd->pos += prtd->pcm_count;
 		spin_unlock_irqrestore(&prtd->lock, flags);
 		snd_pcm_period_elapsed(substream);
-		if (prtd->state == Q6APM_STREAM_RUNNING)
-			q6apm_write_async(prtd->graph, prtd->pcm_count, 0, 0, 0);
 
 		break;
 	case APM_CLIENT_EVENT_DATA_READ_DONE:
@@ -294,6 +293,31 @@ static int q6apm_dai_prepare(struct snd_soc_component *component,
 	return 0;
 }
 
+static int q6apm_dai_ack(struct snd_soc_component *component,
+		struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct q6apm_dai_rtd *prtd = runtime->private_data;
+	unsigned int tail;
+	int i, ret = 0, avail_periods;
+
+	tail = runtime->control->appl_ptr/runtime->period_size;
+
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		avail_periods = tail - prtd->pb_tail;
+		for (i = 0; i < avail_periods; i++) {
+			ret = q6apm_write_async(prtd->graph, prtd->pcm_count, 0, 0, 0);
+			if (ret < 0) {
+				dev_err(component->dev, "Error queuing playback buffer %d\n", ret);
+				return ret;
+			}
+			prtd->pb_tail++;
+		}
+	}
+
+	return ret;
+}
+
 static int q6apm_dai_trigger(struct snd_soc_component *component,
 			     struct snd_pcm_substream *substream, int cmd)
 {
@@ -305,13 +329,11 @@ static int q6apm_dai_trigger(struct snd_soc_component *component,
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-		 /* start writing buffers for playback only as we already queued capture buffers */
-		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
-			ret = q6apm_write_async(prtd->graph, prtd->pcm_count, 0, 0, 0);
 		break;
 	case SNDRV_PCM_TRIGGER_STOP:
 		/* TODO support be handled via SoftPause Module */
 		prtd->state = Q6APM_STREAM_STOPPED;
+		prtd->pb_tail = 0;
 		break;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
@@ -836,6 +858,7 @@ static const struct snd_soc_component_driver q6apm_fe_dai_component = {
 	.hw_params	= q6apm_dai_hw_params,
 	.pointer	= q6apm_dai_pointer,
 	.trigger	= q6apm_dai_trigger,
+	.ack		= q6apm_dai_ack,
 	.compress_ops	= &q6apm_dai_compress_ops,
 	.use_dai_pcm_id = true,
 };
-- 
2.39.5