linux-kernel - Re: [PATCH 2/2] ASoC: fsl: Move clock operation to PM runtime

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Date:   Sat, 20 Apr 2019 22:54:07 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Daniel Baluta <daniel.baluta@....com>
Cc:     "broonie@...nel.org" <broonie@...nel.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "timur@...nel.org" <timur@...nel.org>,
        "Xiubo.Lee@...il.com" <Xiubo.Lee@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "perex@...ex.cz" <perex@...ex.cz>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "S.j. Wang" <shengjiu.wang@....com>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH 2/2] ASoC: fsl: Move clock operation to PM runtime

On Sat, Apr 20, 2019 at 03:59:05PM +0000, Daniel Baluta wrote:
> Turn off/on clocks when device enters suspend/resume. This
> helps saving power.

> @@ -934,6 +933,25 @@ static int fsl_sai_runtime_suspend(struct device *dev)
>  static int fsl_sai_runtime_resume(struct device *dev)
>  {
>  	struct fsl_sai *sai = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = clk_prepare_enable(sai->bus_clk);
> +	if (ret) {
> +		dev_err(dev, "failed to enable bus clock: %d\n", ret);
> +		return ret;
> +	}
> +
> +	if (sai->mclk_streams & BIT(SNDRV_PCM_STREAM_PLAYBACK)) {
> +		ret = clk_prepare_enable(sai->mclk_clk[sai->mclk_id[1]]);
> +		if (ret)
> +			goto disable_bus_clk;
> +	}
> +
> +	if (sai->mclk_streams & BIT(SNDRV_PCM_STREAM_CAPTURE)) {
> +		ret = clk_prepare_enable(sai->mclk_clk[sai->mclk_id[0]]);
> +		if (ret)
> +			goto disable_tx_clk;
> +	}

The driver only enables mclk_clks for I2S master mode. But this
change enables them for I2S slave mode also. It doesn't sound a
right thing to me since we are supposed to save power?