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

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Message-ID: <1555930942.31656.4.camel@nxp.com>
Date:   Mon, 22 Apr 2019 11:02:22 +0000
From:   Viorel Suman <viorel.suman@....com>
To:     "nicoleotsuka@...il.com" <nicoleotsuka@...il.com>,
        Daniel Baluta <daniel.baluta@....com>
CC:     dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "timur@...nel.org" <timur@...nel.org>,
        "Xiubo.Lee@...il.com" <Xiubo.Lee@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "S.j. Wang" <shengjiu.wang@....com>,
        "perex@...ex.cz" <perex@...ex.cz>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>
Subject: Re: [PATCH 2/2] ASoC: fsl: Move clock operation to PM runtime

Hi Nicolin,

On Sb, 2019-04-20 at 22:54 -0700, Nicolin Chen wrote:
> 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?

This change does not enable them for I2S slave mode, please check "fsl_sai_hw_params"
and "fsl_sai_hw_free" functions: the field "sai->mclk_streams" is modified only for
the case when "if (!sai->is_slave_mode)";

Regards,
Viorel