linux-kernel - Re: [PATCH v3 0/4] Clarify abstract scale usage for power values in Energy Model, EAS and IPA

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Date:   Mon, 2 Nov 2020 16:41:57 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Quentin Perret <qperret@...gle.com>
Cc:     Lukasz Luba <lukasz.luba@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Dietmar Eggemann <Dietmar.Eggemann@....com>,
        morten.rasmussen@....com, Matthias Kaehlcke <mka@...omium.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>
Subject: Re: [PATCH v3 0/4] Clarify abstract scale usage for power values in
 Energy Model, EAS and IPA

Hi,

On Mon, Nov 2, 2020 at 5:54 AM Quentin Perret <qperret@...gle.com> wrote:
>
> On Monday 02 Nov 2020 at 08:54:38 (+0000), Lukasz Luba wrote:
> > Gentle ping to Quentin and Daniel for sharing opinion on this patch set.
> > If you are OK, then I could use this as a base for next work.
>
> One or two small nits, but overall this LGTM. Thanks Lukasz.
>
> > As you probably know I am working also on 'sustainable power' estimation
> > which could be used when there is no DT value but it comes from FW.
> > That would meet requirement from Doug, when the DT cannot be used,
> > but we have sustainable levels from FW [1].
>
> Cool, and also, I'd be happy to hear from Doug if passing the sustained
> power via sysfs is good enough for his use-case in the meantime?

It does sound like sysfs could be made to work for us, but it's
definitely a workaround.  If the normal way to set these values was
through sysfs then it would be fine, but I think most people expect
that these values are just setup properly by the kernel.  That means
anyone using our board with a different userspace (someone running
upstream on it) would need to figure out what mechanism they were
going to use to program them.  There's very little advantage here
compared to a downstream patch that just violates official upstream
policy by putting something bogoWatts based in the device tree.

My current plan of record (which I don't love) is basically:

1. Before devices are in consumer's hands, accept bogoWatts numbers in
our downstream kernel.

2. Once devices are in consumers hands, run the script I sent out to
generate some numbers and post them upstream.

If, at some point, there's a better solution then I'll switch to it,
but until then that seems workable even if it makes me grumpy.

-Doug