Re: [PATCH 2/2] PM / devfreq: tie suspend/resume to runtime-pm

From: Rajagopal Venkat
Date: Fri Mar 22 2013 - 05:05:17 EST

On 21 March 2013 20:32, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, 21 Mar 2013, Rajagopal Venkat wrote:
>> Allow device devfreq to be suspend/resume automatically with
>> runtime pm suspend/resume. The devfreq drivers should be least
>> cared when to suspend/resume the devfreq.
>> pm_runtime_suspend(dev) will first suspend device devfreq(if available)
>> before device is suspended from runtime pm core.
>> pm_runtime_resume(dev) will resume device devfreq(if available) after
>> device is resumed from runtime pm core.
> Aren't these backward? The device continues to need its clocks and
> frequency settings until _after_ it has been suspended. Similarly, it
> needs them to be available _before_ it resumes.

To clarify, devfreq suspend/resume means suspend/resume of load
monitoring of a device. The clocks and other resources are still taken
care by the devfreq driver runtime-pm callbacks. The devfreq must be
suspended _before_ runtime-pm suspend callback in order to stop load
monitoring while device is suspending. Similarly devfreq resume should
happen _after_ runtime-pm resume callback.

Just realised both devfreq suspend/resume are done _before_ invoking
runtime-pm callbacks. I will fix this up. Thanks.

> Alan Stern

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