linux-kernel - Re: [PATCH 2/2] PM / devfreq: Use exclusively PM QoS to determine frequency limits

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Date:   Tue, 14 Jan 2020 11:13:53 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Chanwoo Choi <chanwoo@...nel.org>
Cc:     Leonard Crestez <leonard.crestez@....com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH 2/2] PM / devfreq: Use exclusively PM QoS to determine
 frequency limits

On Wed, Jan 15, 2020 at 02:35:48AM +0900, Chanwoo Choi wrote:
> On Wed, Jan 15, 2020 at 1:08 AM Leonard Crestez <leonard.crestez@....com> wrote:
> >
> > On 13.01.2020 09:24, Chanwoo Choi wrote:
> > > Hi,
> > >
> > > Any device driver except for devfreq_cooling.c might
> > > use dev_pm_opp_enable/disable interface.
> > > So, don't need to remove the devfreq->scaling_max_freq
> > > and devfreq->scaling_min_freq for supporting OPP interface.
> >
> > It seems that devfreq_cooling was the only upstream user of
> > dev_pm_opp_enable and the remaining callers of dev_pm_opp_disable are
> > probe-time checks.
> 
> OPP interface has still dev_pm_opp_enable and dev_pm_opp_disable
> function. As long as remains them, any device driver related to devfreq
> could call them at some time. The devfreq supports the OPP interface,
> not just for only devfreq_cooling.

I would like to remove the disabled OPP handling since no devfreq device
makes use of dev_pm_opp_enable/disable, but I fear you are right that
we have to keep it as long as the API is available.