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 17:28:36 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.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 22 October 2014 17:09, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> Hi Ulf,
>
> 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.
>
> Are you trying to repeat power-up-all-PM-domains-during-boot for
> clocks, too? ;-)

This is related, but there are a difference. :-)

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?

Kind regards
Uffe
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