Re: [PATCH 03/14] ASoC: sun4i-i2s: Add apb reset

Maxime Ripard
2016-10-04T15:42:18Z

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Hi,

On Tue, Oct 04, 2016 at 02:15:16PM +0200, Thomas Petazzoni wrote:
> Hello,
>
> On Tue, 4 Oct 2016 11:46:16 +0200, Mylène Josserand wrote:
>
> > #include <sound/dmaengine_pcm.h>
> > #include <sound/pcm_params.h>
> > @@ -589,6 +590,7 @@ static int sun4i_i2s_probe(struct platform_device *pdev)
> > {
> > struct sun4i_i2s *i2s;
> > struct resource *res;
> > + struct reset_control *reset_apb;
> > void __iomem *regs;
> > int irq, ret;
> >
> > @@ -626,7 +628,19 @@ static int sun4i_i2s_probe(struct platform_device *pdev)
> > dev_err(&pdev->dev, "Can't get our mod clock\n");
> > return PTR_ERR(i2s->mod_clk);
> > }
> > -
> > +
> > + reset_apb = devm_reset_control_get(&pdev->dev, "apb_reset");
>
> I believe this is a change in the Device Tree binding, since you're
> adding support for a new resource. Perhaps the Device Tree binding
> documentation should be updated accordingly?

Indeed.

You have two solutions to do that:
- Either mark it as optional and use reset_control_get_optional
(because here, you broke the other SoCs that have that controller
but no reset line)
- Or introduce a new compatible, and make the reset property
mandatory for that new compatible.

I prefer the latter, since you get a stricter error check, and you
cannot end up in a situation where your driver probes but is
useless. But you'll find both in our drivers.

> > + }
> > +
> > + ret = reset_control_deassert(reset_apb);
> > + if (ret < 0) {
> > + dev_err(&pdev->dev, "Can't deassert apb reset (%d)\n", ret);
> > + return ret;
> > + }
>
> Do you need to re-assert the reset line in the ->remove() hook?

Even better, you can add it to the runtime_pm hooks! :)

Maxime

--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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