linux-kernel - Re: [RFC V7 2/2] OPP: Allow "opp-hz" and "opp-microvolt" to contain magic values

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Message-ID: <CAKohpokvQD4Z6YY6MRG8c+hnsS=Z52X4XhyTgC5FTgf7VuaNmw@mail.gmail.com>
Date:   Wed, 1 Nov 2017 02:17:57 +0000
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Kevin Hilman <khilman@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Sudeep Holla <sudeep.holla@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC V7 2/2] OPP: Allow "opp-hz" and "opp-microvolt" to contain
 magic values

On 31 October 2017 at 16:02, Rob Herring <robh+dt@...nel.org> wrote:
> Why not a new property for magic values? opp-magic? Don't we want to
> know when we have magic values?

I have kept a separate property since beginning (domain-performance-state)
and moved to using these magic values in the existing field because of the
suggestion Kevin gave earlier.

https://marc.info/?l=linux-kernel&m=149306082218001&w=2

I am not sure what to do now :)

> Wouldn't magic values in opp-hz get propagated to user space?

The OPP core puts them in debugfs just to know how the OPPs are
set. Otherwise, I am not sure that the power domain core/drivers would
be exposing that to user space.

> I can
> see the complaints now. "My 4GHz processor is running at 6Hz!" Just
> like people complain when BogoMIPS is not high enough.

Hmm, would adding the right user type in bindings would be good enough
for that? I mean, we can clearly add that only power-domains that are
managed by firmware are allowed to use magic values here. But not sure
if we should put such stuff in bindings.

--
viresh