Subject: Re: [PATCH 2/2] ASoC: fsl: Move clock operation to PM runtime

From: Viorel Suman <[email-masked]>
Date: Mon, 22 Apr 2019 11:02:22 +0000

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