linux-kernel - Re: [PATCH 1/2] thermal: cooling: Check Energy Model type in cpufreq_cooling and devfreq

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Date:   Wed, 16 Feb 2022 09:21:19 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     Matthias Kaehlcke <mka@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        amit daniel kachhap <amit.kachhap@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Pierre.Gondois@....com, Stephen Boyd <swboyd@...omium.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH 1/2] thermal: cooling: Check Energy Model type in
 cpufreq_cooling and devfreq_cooling

Hi,

On Tue, Feb 8, 2022 at 1:32 AM Lukasz Luba <lukasz.luba@....com> wrote:
>
> >    Another important thing is the consistent scale of the power values
> >    provided by the cooling devices. All of the cooling devices in a single
> >    thermal zone should have power values reported either in milli-Watts
> >    or scaled to the same 'abstract scale'.
>
> This can change. We have removed the userspace governor from kernel
> recently. The trend is to implement thermal policy in FW. Dealing with
> some intermediate configurations are causing complicated design, support
> of the algorithm logic is also more complex.

One thing that didn't get addressed is the whole "The trend is to
implement thermal policy in FW". I'm not sure I can get on board with
that trend. IMO "moving to FW" isn't a super great trend. FW is harder
to update than kernel and trying to keep it in sync with the kernel
isn't wonderful. Unless something _has_ to be in FW I personally
prefer it to be in the kernel.

...although now that I re-read this, I'm not sure which firmware you
might be talking about. Is this the AP firmware, or some companion
chip / coprocessor? Even so, I'd still rather see things done in the
kernel when possible...

-Doug