From: Lukasz Luba <lukasz.luba@arm.com>
To: Doug Anderson <dianders@chromium.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
linux-doc@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Dietmar.Eggemann@arm.com, Quentin Perret <qperret@google.com>,
Matthias Kaehlcke <mka@chromium.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Rajendra Nayak <rnayak@codeaurora.org>
Subject: Re: [PATCH 1/2] docs: Clarify abstract scale usage for power values in Energy Model
Date: Wed, 30 Sep 2020 09:25:21 +0100 [thread overview]
Message-ID: <a1d1fe2a-485f-a21e-2f91-9b609223aa5a@arm.com> (raw)
In-Reply-To: <CAD=FV=UnNkjMiOc0DZE7+OM3-Kr1ZRynxSerdA=ifbyGiRa2Zw@mail.gmail.com>
Hi Douglas,
On 9/30/20 12:53 AM, Doug Anderson wrote:
> Hi,
>
> On Tue, Sep 29, 2020 at 5:16 AM Lukasz Luba <lukasz.luba@arm.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@arm.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@chromium.org>
Thank you for the review.
>
> 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?
For completeness, we are talking here about the binding from:
Documentation/devicetree/bindings/arm/cpus.yaml
which is 'dynamic-power-coefficient'. Yes, it stays untouched, also the
unit (uW/MHz/V^2) which then allows to have mW in the power
values in the EM.
Regards,
Lukasz
next prev parent reply other threads:[~2020-09-30 8:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-29 12:16 [PATCH 1/2] docs: Clarify abstract scale usage for power values in Energy Model Lukasz Luba
2020-09-29 12:16 ` [PATCH 2/2] PM / EM: update the comments related to power scale Lukasz Luba
2020-09-29 23:53 ` [PATCH 1/2] docs: Clarify abstract scale usage for power values in Energy Model Doug Anderson
2020-09-30 8:25 ` Lukasz Luba [this message]
2020-09-30 10:55 ` Rajendra Nayak
2020-09-30 14:04 ` Lukasz Luba
2020-09-30 15:48 ` Rajendra Nayak
2020-09-30 17:24 ` Doug Anderson
2020-10-01 14:09 ` Lukasz Luba
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