[PATCH v3] ASoC: qcom: lpass-cpu: Fix pop noise during audio capture begin

[Srinivasa Rao Mandadapu <srivasam@xxxxxxxxxxxxxx>]

This patch fixes PoP noise of around 15ms observed during audio capture begin.
Enables BCLK and LRCLK in snd_soc_dai_ops prepare call for introducing some delay
before capture start and clock enable.

Co-developed-by: Judy Hsiao <judyhsiao@xxxxxxxxxxxx>
Signed-off-by: Judy Hsiao <judyhsiao@xxxxxxxxxxxx>
Signed-off-by: Srinivasa Rao Mandadapu <srivasam@xxxxxxxxxxxxxx>
---
Changes Since V2:
	-- Updated comments as per linux style
	-- Removed unrelated changes. 
Changes Since V1:
	-- Enableed BCLK and LRCLK in dai ops prepare API instead of startup API
	-- Added comments

 sound/soc/qcom/lpass-cpu.c | 54 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

diff --git a/sound/soc/qcom/lpass-cpu.c b/sound/soc/qcom/lpass-cpu.c
index 28c7497344e3..1855eae22aad 100644
--- a/sound/soc/qcom/lpass-cpu.c
+++ b/sound/soc/qcom/lpass-cpu.c
@@ -93,9 +93,21 @@ static void lpass_cpu_daiops_shutdown(struct snd_pcm_substream *substream,
 		struct snd_soc_dai *dai)
 {
 	struct lpass_data *drvdata = snd_soc_dai_get_drvdata(dai);
+	struct lpaif_i2sctl *i2sctl = drvdata->i2sctl;
+	unsigned int id = dai->driver->id;
 
 	clk_disable_unprepare(drvdata->mi2s_osr_clk[dai->driver->id]);
-	clk_unprepare(drvdata->mi2s_bit_clk[dai->driver->id]);
+	/*
+	 * To ensure BCLK/LRCLK disabled even in device node validation
+	 * Will not impact if disabled in lpass_cpu_daiops_trigger()
+	 * suspend.
+	 */
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		regmap_fields_write(i2sctl->spken, id, LPAIF_I2SCTL_SPKEN_DISABLE);
+	else
+		regmap_fields_write(i2sctl->micen, id, LPAIF_I2SCTL_MICEN_DISABLE);
+
+	clk_disable_unprepare(drvdata->mi2s_bit_clk[dai->driver->id]);
 }
 
 static int lpass_cpu_daiops_hw_params(struct snd_pcm_substream *substream,
@@ -275,6 +287,10 @@ static int lpass_cpu_daiops_trigger(struct snd_pcm_substream *substream,
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+		/*
+		 * To ensure lpass BCLK/LRCLK is enabled during
+		 * device resume. Will not impact if enabled in lpass_cpu_daiops_prepare().
+		 */
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 			ret = regmap_fields_write(i2sctl->spken, id,
 						 LPAIF_I2SCTL_SPKEN_ENABLE);
@@ -296,6 +312,10 @@ static int lpass_cpu_daiops_trigger(struct snd_pcm_substream *substream,
 	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
+		/*
+		 * To ensure lpass BCLK/LRCLK is disabled during
+		 * device suspend.
+		 */
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 			ret = regmap_fields_write(i2sctl->spken, id,
 						 LPAIF_I2SCTL_SPKEN_DISABLE);
@@ -315,12 +335,44 @@ static int lpass_cpu_daiops_trigger(struct snd_pcm_substream *substream,
 	return ret;
 }
 
+static int lpass_cpu_daiops_prepare(struct snd_pcm_substream *substream,
+		struct snd_soc_dai *dai)
+{
+	struct lpass_data *drvdata = snd_soc_dai_get_drvdata(dai);
+	struct lpaif_i2sctl *i2sctl = drvdata->i2sctl;
+	unsigned int id = dai->driver->id;
+	int ret;
+	/*
+	 * To ensure lpass BCLK/LRCLK is enabled bit before
+	 * playback/capture data flow starts.
+	 */
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		ret = regmap_fields_write(i2sctl->spken, id, LPAIF_I2SCTL_SPKEN_ENABLE);
+	else
+		ret = regmap_fields_write(i2sctl->micen, id, LPAIF_I2SCTL_MICEN_ENABLE);
+
+	if (ret) {
+		dev_err(dai->dev, "error writing to i2sctl reg: %d\n", ret);
+		return ret;
+	}
+
+	ret = clk_enable(drvdata->mi2s_bit_clk[id]);
+
+	if (ret) {
+		dev_err(dai->dev, "error in enabling mi2s bit clk: %d\n", ret);
+		clk_disable(drvdata->mi2s_osr_clk[id]);
+		return ret;
+	}
+	return 0;
+}
+
 const struct snd_soc_dai_ops asoc_qcom_lpass_cpu_dai_ops = {
 	.set_sysclk	= lpass_cpu_daiops_set_sysclk,
 	.startup	= lpass_cpu_daiops_startup,
 	.shutdown	= lpass_cpu_daiops_shutdown,
 	.hw_params	= lpass_cpu_daiops_hw_params,
 	.trigger	= lpass_cpu_daiops_trigger,
+	.prepare	= lpass_cpu_daiops_prepare,
 };
 EXPORT_SYMBOL_GPL(asoc_qcom_lpass_cpu_dai_ops);
 
-- 
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