linux-kernel - Re: [PATCH v4 2/3] devfreq: Add suspend and resume apis

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Message-ID: <13521737.MW7piF1i8B@vostro.rjw.lan>
Date:	Mon, 15 Oct 2012 22:43:51 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	myungjoo.ham@...sung.com
Cc:	Rajagopal Venkat <rajagopal.venkat@...aro.org>,
	"mturquette@...aro.org" <mturquette@...aro.org>,
	박경민 <kyungmin.park@...sung.com>,
	"patches@...aro.org" <patches@...aro.org>,
	"linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/3] devfreq: Add suspend and resume apis

On Monday 08 of October 2012 10:48:24 MyungJoo Ham wrote:
> > On 8 October 2012 03:31, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > On Thursday 04 of October 2012 14:58:33 Rajagopal Venkat wrote:
> > >> Add devfreq suspend/resume apis for devfreq users. This patch
> > >> supports suspend and resume of devfreq load monitoring, required
> > >> for devices which can idle.
> > >>
> > >> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@...aro.org>
> > >> Acked-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> > >
> > > Well, I wonder if this may be tied in to the runtime PM framework, so that,
> > > for example, pm_runtime_suspend() will automatically suspend devfreq on
> > > success (and the runtime resume of the device will resume devfreq)?
> > 
> > That's a good idea. If you agree, we can handle this as separate patch on
> > top this patchset.

Sure.

> I guess implementing the idea may be not so obvious; thus, seperating
> the patchset would be appropriate.
> 
> When we implement the idea, we may need to implement at the
> pm_runtime core. Because devfreq->dev is a child of the target dev, not
> a parent, runtime-pm event of the target dev does not automatically
> invoke a cascaded action on the devfreq->dev.

I'm not exactly sure what you mean, care to explain?

> Maybe either
> 1) capability to allow a child to monitor the power state of a parent
> (I remember Inki Dae once suggested to add notifiers at runtime-pm, but
> it seems to be not merged)
> or
> 2) letting runtime-pm be aware of devfreq
> (doesn't feel alright with this??)
> is required?

I'm not a big fan of notifiers, so I'd prefer to avoid using them, if
possible.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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