linux-kernel - Re: [PATCH 2/7] cpufreq: dt: Register an Energy Model

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Date:   Tue, 29 Jan 2019 09:15:49 +0000
From:   Quentin Perret <quentin.perret@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Matthias Kaehlcke <mka@...omium.org>, rjw@...ysocki.net,
        sudeep.holla@....com, liviu.dudau@....com,
        lorenzo.pieralisi@....com, robh+dt@...nel.org,
        mark.rutland@....com, nm@...com, sboyd@...nel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dietmar.eggemann@....com
Subject: Re: [PATCH 2/7] cpufreq: dt: Register an Energy Model

On Tuesday 29 Jan 2019 at 10:51:44 (+0530), Viresh Kumar wrote:
> On 28-01-19, 11:36, Matthias Kaehlcke wrote:
> > I think this patch will result in error messages at registration on
> > platforms that use the cpufreq-dt driver and don't specify
> > 'dynamic-power-coefficient' for the CPUs in the DT. Not sure if that's
> > a problem as long as the cpufreq initialization succeeds regardless,
> > it could be seen as a not-so-gentle nudge to add the values.
> 
> That wouldn't be acceptable.

Fair enough. What I can propose in this case is to have in PM_OPP a
helper called 'dev_pm_opp_of_register_em()' or something like this. This
function will check all prerequisites are present (we have the right
values in DT, and so on) and then call (or not) em_register_perf_domain().
Then we can make the CPUFreq drivers use that instead of calling
em_register_perf_domain() directly.

That would also make it easy to implement Matthias' suggestion to not
call em_register_perf_domain() if an EM is already present.

Would that work ?

Thanks,
Quentin