linux-kernel - Re: [PATCH v2 0/3] Clarify abstract scale usage for power values in Energy Model, EAS and IPA

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Date:   Fri, 16 Oct 2020 17:02:18 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Dietmar Eggemann <Dietmar.Eggemann@....com>,
        Doug Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        "Nayak, Rajendra" <rnayak@...eaurora.org>
Subject: Re: [PATCH v2 0/3] Clarify abstract scale usage for power values in
 Energy Model, EAS and IPA

On Friday 16 Oct 2020 at 15:42:57 (+0100), Lukasz Luba wrote:
> Do you mean a new entry in DT which will be always below
> 'dynamic-power-coefficient' and/or 'sustainable-power' saying the unit
> of above value?

Yes, something like that.

> There was discussion with Rob (and Doug) about this. I got the
> impression he was against any new DT stuff [1].
> We don't have to, I think we all agree that DT will only support mW.

Right, I agree this is a 'nice-to-have'.

> I have agreed to this idea having a 'flag' inside EM [2], which
> indicates the mW or bogoWatts. It could be set via API:
> em_dev_register_perf_domain() and this new last argument.
> 
> I can write that patch. There is only two usage (3rd is on LKML) of
> that function. The DT way, which is via:
> dev_pm_opp_of_register_em() will always set 'true';
> Driver direct calls of em_dev_register_perf_domain(), will have to
> set appropriate value ('true' or 'false'). The EM struct em_perf_domain
> will have the new bool field set based on that.
> Is it make sense?

I had something more complicated in mind, where units are arbitrary
('milliwats', 'scmi-bogowatts', ...) as that would help if units can be
specified in the DT too, but if we don't care about that then yes I
suppose a boolean flag should do.

Thanks!
Quentin