linux-kernel - Re: [PATCH 0/3] drivers: Frequency constraint infrastructure

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Date:   Fri, 11 Jan 2019 10:47:37 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] drivers: Frequency constraint infrastructure

On Fri, Jan 11, 2019 at 10:18 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> Hi,
>
> This commit introduces the frequency constraint infrastructure, which
> provides a generic interface for parts of the kernel to constraint the
> working frequency range of a device.
>
> The primary users of this are the cpufreq and devfreq frameworks. The
> cpufreq framework already implements such constraints with help of
> notifier chains (for thermal and other constraints) and some local code
> (for user-space constraints). The devfreq framework developers have also
> shown interest [1] in such a framework, which may use it at a later
> point of time.
>
> The idea here is to provide a generic interface and get rid of the
> notifier based mechanism.
>
> Only one constraint is added for now for the cpufreq framework and the
> rest will follow after this stuff is merged.
>
> Matthias Kaehlcke was involved in the preparation of the first draft of
> this work and so I have added him as Co-author to the first patch.
> Thanks Matthias.
>
> FWIW, This doesn't have anything to do with the boot-constraints
> framework [2] I was trying to upstream earlier :)

This is quite a bit of code to review, so it will take some time.

One immediate observation is that it seems to do quite a bit of what
is done in the PM QoS framework, so maybe there is an opportunity for
some consolidation in there.

Cheers,
Rafael