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

Mylene Josserand
2016-10-05T09:43:10Z

Hello,

On 04/10/2016 17:42, Maxime Ripard wrote:
> 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.
>

Okay, thank you for the hints!

>>> + }
>>> +
>>> + 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! :)

I will have a look to runtime_pm and update it for a V2.

--
Mylène Josserand, Free Electrons
Embedded Linux and Kernel engineering