Re: [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq

[Åukasz Majewski]

On 09/05/2017 09:52 AM, Nicolin Chen wrote:
> On Tue, Sep 05, 2017 at 09:37:43AM +0200, Åukasz Majewski wrote:
>
> > > > The last call is changing the bit clock (BCLK) frequency to SSI's IP
> > > > block clock (ipg = 66 MHz) [1].
> > >
> > > I think a bigger question here is why the routine sets BCLK to 66MHz.
> >
> > Yes, exactly.
> >
> > In my case the bclk is set to ipg clock, which is the SSI IP block clock
> > (ipg).
>
> Can you elaborate why you set ipg clock as bclk? I don't remember SSI could
> derive bitclock from ipg clock.

Just to be clear:

What clock shall be set with:

struct snd_soc_dai_ops {

	int (*set_sysclk)(struct snd_soc_dai *dai,
		int clk_id, unsigned int freq, int dir);
}

callback?

The SSI IP block or BCLK ?


> > > > This is wrong, since IMX SSI block requires the I2S BCLK to be less
> > > > than 1/5 of [1].
> > > >
> > > > As a result the driver initialization passes without any errors, but the
> > > > speaker-test test case breaks.
> > > >
> > > > This commit checks if the fsl_ssi_set_dai_sysclk() frequency passed is
> > > > not equal to [1].
> > >
> > > I don't feel it's quite comprehensive...what if it's being set to 67MHz.
> >
> > I think that this clock is not changing for the SoC. It should be 66 MHz
> > fixed.
>
> What I mean is that we cannot just look at this SoC. Today is 66MHz for this
> SoC. Tomorrow could be 133MHz for another one. We should put a check that none
> of these shall pass -- the 1/5 limit.

Ok. Good point.


--
Best regards,

Lukasz Majewski

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