linux-kernel - Re: [PATCH v2 2/3] ARM: keystone: pm: switch to use generic pm domains

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Date:	Wed, 22 Oct 2014 17:44:30 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	Grygorii Strashko <grygorii.strashko@...com>,
	Santosh Shilimkar <santosh.shilimkar@...il.com>,
	ssantosh@...nel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
	Kevin Hilman <khilman@...aro.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] ARM: keystone: pm: switch to use generic pm domains

On Wed, Oct 22, 2014 at 5:28 PM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> On 22 October 2014 17:09, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>> On Wed, Oct 22, 2014 at 5:01 PM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
>>>>>> +void keystone_pm_domain_attach_dev(struct device *dev)
>>>>>>   {
>>>>>> +    struct clk *clk;
>>>>>>       int ret;
>>>>>> +    int i = 0;
>>>>>>
>>>>>>       dev_dbg(dev, "%s\n", __func__);
>>>>>>
>>>>>> -    ret = pm_generic_runtime_suspend(dev);
>>>>>> -    if (ret)
>>>>>> -        return ret;
>>>>>> -
>>>>>> -    ret = pm_clk_suspend(dev);
>>>>>> +    ret = pm_clk_create(dev);
>>>>>>       if (ret) {
>>>>>> -        pm_generic_runtime_resume(dev);
>>>>>> -        return ret;
>>>>>> +        dev_err(dev, "pm_clk_create failed %d\n", ret);
>>>>>> +        return;
>>>>>> +    };
>>>>>> +
>>>>>> +    while ((clk = of_clk_get(dev->of_node, i++)) && !IS_ERR(clk)) {
>>>>>> +        ret = pm_clk_add_clk(dev, clk);
>>>>>> +        if (ret) {
>>>>>> +            dev_err(dev, "pm_clk_add_clk failed %d\n", ret);
>>>>>> +            goto clk_err;
>>>>>> +        };
>>>>>>       }
>>>>>>
>>>>>> -    return 0;
>>>>>> +    if (!IS_ENABLED(CONFIG_PM_RUNTIME)) {
>>>>> Can we not okkup two seperate callbacks instead of above check ?
>>>>> I don't like this CONFIG check here. Its slightly better version of
>>>>> ifdef in middle of the code.
>>>>
>>>> I've found more-less similar comment on patch
>>>> "Re: [PATCH v3 1/3] power-domain: add power domain drivers for Rockchip platform"
>>>> https://lkml.org/lkml/2014/10/17/257
>>>>
>>>> So, Would you like me to create patch which will enable clocks in pm_clk_add/_clk()
>>>> in case !IS_ENABLED(CONFIG_PM_RUNTIME)
>>>
>>> I am wondering whether we actually should/could do this, no matter of
>>> CONFIG_PM_RUNTIME.
>>>
>>> Typically, for configurations that uses CONFIG_PM_RUNTIME, the PM
>>> clocks through pm_clk_suspend(), will be gated once the device becomes
>>> runtime PM suspended. Right?
>>
>> Doing it unconditionally means we'll have lots of unneeded clocks running
>> for a short while.

> As long as the pm_clk_add() is being invoked from the ->attach_dev()
> callback, we are in the probe path. Certainly we would like to have
> clocks enabled while probing, don't you think?
>
> If we wouldn't enable the clocks for CONFIG_PM_RUNTIME, when will
> those be enabled?

They will be enabled when the driver does

        pm_runtime_enable(dev);
        pm_runtime_get_sync(dev);

in its .probe() method.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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