On Mon, Nov 04, 2013 at 07:35:12AM +0000, Li Xiubo wrote: > From the ASoC subsystem comments we can see that: > ++++++ > Configures the clock dividers. This is used to derive the best DAI bit and > frame clocks from the system or master clock. It's best to set the DAI bit > and frame clocks as low as possible to save system power. > ------
You should never use this unless you have to, there is no point in every
single machine driver using your driver having to duplicate the same
calculations.
>
> > > +static int fsl_sai_dai_probe(struct snd_soc_dai *dai) {
> > > + int ret;
> > > + struct fsl_sai *sai = dev_get_drvdata(dai->dev);
> > > +
> > > + ret = clk_prepare_enable(sai->clk);
> > > + if (ret)
> > > + return ret;
> > It'd be nicer to only enable the clock while the device is in active use.
> While if the module clock is not enabled here, the followed registers cannot
> read/write in the same function.
> And this _probe function is the _dai_probe not the driver's module _probe.
So you can enable the clock when you explicitly need to write to the
registers...
> If the clk_prepare_enable(sai->clk) is not here, where should it be will be
> nicer ?
> One of the following functions ?
> .set_sysclk = fsl_sai_set_dai_sysclk,
> .set_clkdiv = fsl_sai_set_dai_clkdiv,
> .set_fmt = fsl_sai_set_dai_fmt,
> .set_tdm_slot = fsl_sai_set_dai_tdm_slot,
> .hw_params = fsl_sai_hw_params,
> .trigger = fsl_sai_trigger,
It could be in any or all of them except trigger (where the core should
hold a runtime PM reference anyway). You can always take a reference
for the duration of the function if you're concerned it may be called
when the referent isn't otherwise held.
> > > + ret = snd_dmaengine_pcm_register(&pdev->dev, NULL,
> > > + SND_DMAENGINE_PCM_FLAG_NO_RESIDUE);
> > > + if (ret)
> > > + return ret;
> > We should have a devm_ version of this.
> Sorry, is there one patch for adding the devm_ version of
> snd_dmaengine_pcm_register() already ?
> In the -next and other topics branches I could not find it.
No, there isn't one but there should be one.
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