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

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Message-ID: <CA+Z25wXYprpAOChV2P1vfbTgUyd7Te5s3RCmTLLaez6qiTx5GA@mail.gmail.com>
Date:	Fri, 22 Mar 2013 14:35:07 +0530
From:	Rajagopal Venkat <rajagopal.venkat@...aro.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	myungjoo.ham@...sung.com, rjw@...k.pl,
	Kevin Hilman <khilman@...aro.org>,
	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] PM / devfreq: tie suspend/resume to runtime-pm

On 21 March 2013 20:32, Alan Stern <stern@...land.harvard.edu> 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
>



-- 
Regards,
Rajagopal
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