linux-kernel - Re: [PATCH 1/2] docs: Clarify abstract scale usage for power values in Energy Model

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Message-ID: <CAD=FV=UnNkjMiOc0DZE7+OM3-Kr1ZRynxSerdA=ifbyGiRa2Zw@mail.gmail.com>
Date:   Tue, 29 Sep 2020 16:53:12 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>, linux-doc@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Dietmar.Eggemann@....com, Quentin Perret <qperret@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rajendra Nayak <rnayak@...eaurora.org>
Subject: Re: [PATCH 1/2] docs: Clarify abstract scale usage for power values
 in Energy Model

Hi,

On Tue, Sep 29, 2020 at 5:16 AM Lukasz Luba <lukasz.luba@....com> wrote:
>
> The Energy Model (EM) can store power values in milli-Watts or in abstract
> scale. This might cause issues in the subsystems which use the EM for
> estimating the device power, such as:
> - mixing of different scales in a subsystem which uses multiple
>   (cooling) devices (e.g. thermal Intelligent Power Allocation (IPA))
> - assuming that energy [milli-Joules] can be derived from the EM power
>   values which might not be possible since the power scale doesn't have to
>   be in milli-Watts
>
> To avoid misconfiguration add the needed documentation to the EM and
> related subsystems: EAS and IPA.
>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
>  .../driver-api/thermal/power_allocator.rst          |  8 ++++++++
>  Documentation/power/energy-model.rst                | 13 +++++++++++++
>  Documentation/scheduler/sched-energy.rst            |  5 +++++
>  3 files changed, 26 insertions(+)

I haven't read through these files in massive detail, but the quick
skim makes me believe that your additions seem sane.  In general, I'm
happy with documenting reality, thus:

Reviewed-by: Douglas Anderson <dianders@...omium.org>

I will note: you haven't actually updated the device tree bindings.
Thus, presumably, anyone who is specifying these numbers in the device
tree is still supposed to specify them in a way that mW can be
recovered, right?  Said another way: nothing about your patches makes
it OK to specify numbers in device trees using an "abstract scale",
right?

-Doug