Re: [v6] ASoC: qcom: lpass-cpu: Fix pop noise during audio capture begin

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

On 04/06/2021 08:11, Judy Hsiao wrote:
> +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;
> +
> +	/*
> +	 * Ensure lpass BCLK/LRCLK is enabled bit before playback/capture
> +	 * data flow starts. This allows other codec to have some delay before
> +	 * the data flow.
> +	 * (ex: to drop start up pop noise before capture 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;
> +	}
> +
> +	/*
> +	 * Check mi2s_was_prepared before enabling BCLK as lpass_cpu_daiops_prepare can
> +	 * be called multiple times. It's paired with the clk_disable in
> +	 * lpass_cpu_daiops_shutdown.
> +	 */
> +	if (!drvdata->mi2s_was_prepared[dai->driver->id]) {
> +		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]);

This disable is not required, as failure of prepare will result in 
calling shutdown which should take care of this. If not you will be 
disabling clk twice.

Other than that patch looks good to me!

--srini


> +			return ret;
> +		}
> +		drvdata->mi2s_was_prepared[dai->driver->id] = true;
> +	}
> +	return 0;
> +}
> +