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

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Message-ID: <20140910062118.GA26348@pengutronix.de>
Date:	Wed, 10 Sep 2014 08:21:18 +0200
From:	Markus Pargmann <mpa@...gutronix.de>
To:	Nicolin Chen <nicoleotsuka@...il.com>
Cc:	Shengjiu Wang <shengjiu.wang@...escale.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 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

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