linux-kernel - Re: [PATCH V1] ASoC: fsl_ssi: refine ipg clock usage in this module

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Date:	Wed, 10 Sep 2014 18:30:06 +0800
From:	Shengjiu Wang <shengjiu.wang@...escale.com>
To:	Markus Pargmann <mpa@...gutronix.de>
CC:	Nicolin Chen <nicoleotsuka@...il.com>, <timur@...i.org>,
	<Li.Xiubo@...escale.com>, <lgirdwood@...il.com>,
	<broonie@...nel.org>, <perex@...ex.cz>, <tiwai@...e.de>,
	<alsa-devel@...a-project.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V1] ASoC: fsl_ssi: refine ipg clock usage in this module

On Wed, Sep 10, 2014 at 08:21:18AM +0200, Markus Pargmann wrote:
> On Tue, Sep 09, 2014 at 11:38:05AM -0700, Nicolin Chen wrote:
> > On Tue, Sep 09, 2014 at 05:18:07PM +0800, Shengjiu Wang wrote:
> > > @@ -1321,7 +1333,11 @@ static int fsl_ssi_probe(struct platform_device *pdev)
> > >  		return -ENOMEM;
> > >  	}
> > >  
> > > -	ssi_private->regs = devm_regmap_init_mmio(&pdev->dev, iomem,
> > > +	if (ssi_private->soc->imx)
> > > +		ssi_private->regs = devm_regmap_init_mmio_clk(&pdev->dev,
> > > +			"ipg", iomem, &fsl_ssi_regconfig);
> > > +	else
> > > +		ssi_private->regs = devm_regmap_init_mmio(&pdev->dev, iomem,
> > 
> > As Markus mentioned, the key point here is to be compatible with those
> > non-clock-name platforms.
> > 
> > I think it would be safer to keep the current code while adding an extra
> > clk_disable_unprepare() at the end of probe() as a common routine. And
> > meantime, make sure to have the call for imx only because it seems that
> > the other platforms do not depend on the clock. //a bit guessing here :)
> > 
> > Then we can get a patch like:
> > open() {
> > +	clk_prepare_enable();
> > 	....
> > }
> > 
> > close() {
> > 	....
> > +	clk_disable_unprepare()
> > }
> > 
> > probe() {
> > 	clk_get();
> > 	clk_prepare_enable();
> > 	....
> > 	if (xxx)
> > -		goto err_xx;
> > +		return ret;
> > 	....
> > +	clk_disable_unprepare();
> > 	return 0;
> > -err_xx:
> > -	clk_disable_unprepare()
> > }
> > 
> > remove() {
> > 	....
> > -	clk_disable_unprepare()
> > }
> 
> If I remember correctly, there may be AC97 communication with the codec
> before any substream is created. That's why we enable the SSI unit right
> at the beginning for AC97 in fsl_ssi_setup_reg_vals(). So we need to
> check for AC97 before disabling clocks.
> 
> Best regards,
> 
> Markus

hi Markus

I think if clk_prepare_enable() in startup(), and clk_disable_unprepare()
in shutdown can meet this requirement, right?


done:
        if (ssi_private->dai_fmt)
                _fsl_ssi_set_dai_fmt(ssi_private, ssi_private->dai_fmt);

I find that in end of probe, there is setting of dai_fmt. Can we remove this?
because this setting need to enable ipg clock, and if ac97, ipg clock can't be
disabled.

wang shengjiu
> 
> -- 
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