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

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Date:   Fri, 28 May 2021 09:47:56 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Srinivasa Rao Mandadapu <srivasam@...eaurora.org>,
        agross@...nel.org, bjorn.andersson@...aro.org, lgirdwood@...il.com,
        broonie@...nel.org, robh+dt@...nel.org, plai@...eaurora.org,
        bgoswami@...eaurora.org, perex@...ex.cz, tiwai@...e.com,
        rohitkr@...eaurora.org, linux-arm-msm@...r.kernel.org,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, swboyd@...omium.org,
        judyhsiao@...omium.org
Subject: Re: [PATCH v3] ASoC: qcom: lpass-cpu: Fix pop noise during audio
 capture begin



On 24/05/2021 15:21, Srinivasa Rao Mandadapu wrote:
> 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@...omium.org>
> Signed-off-by: Judy Hsiao <judyhsiao@...omium.org>
> Signed-off-by: Srinivasa Rao Mandadapu <srivasam@...eaurora.org>
> ---
> 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().
> +		 */

prepare should have already ensured that isn't it?


>   		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;
>   }
>   


[Snip ...
> +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;
> +}
> +
----]

If prepare is enabling the clk and the i2s enable bits, then why do we 
need to do the same thing in trigger?

Also the clk enable count is going up twice (once in prepare and 
trigger) and we can never be able to disable the clk as there is is no 
corresponding disable for this prepare path.

Also note that prepare can be called multiple times.

--srini

>   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);
>   
>