linux-kernel - Re: [PATCH v10 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model

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Date:   Thu, 10 Jan 2019 09:08:47 +0000
From:   Quentin Perret <quentin.perret@....com>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     peterz@...radead.org, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        gregkh@...uxfoundation.org, mingo@...hat.com,
        dietmar.eggemann@....com, morten.rasmussen@....com,
        chris.redpath@....com, patrick.bellasi@....com,
        valentin.schneider@....com, vincent.guittot@...aro.org,
        thara.gopinath@...aro.org, viresh.kumar@...aro.org,
        tkjos@...gle.com, joel@...lfernandes.org, smuckle@...gle.com,
        adharmap@...eaurora.org, skannan@...eaurora.org,
        pkondeti@...eaurora.org, juri.lelli@...hat.com,
        edubezval@...il.com, srinivas.pandruvada@...ux.intel.com,
        currojerez@...eup.net, javi.merino@...nel.org
Subject: Re: [PATCH v10 15/15] OPTIONAL: cpufreq: dt: Register an Energy Model

On Wednesday 09 Jan 2019 at 10:14:51 (-0800), Matthias Kaehlcke wrote:
> I think registering the perf domain only once is fine, since the info
> isn't supposed to change and will likely be used again after
> _exit(). However since we have em_cpu_get() I'd suggest to use it and
> only call em_register_perf_domain() if no perf domain is registered
> yet for the CPU. This makes it more evident that the registration is
> only done once and simplifies error handling (currently not done at
> all), since it's not necessary to check for the special case -EEXIST.

Right, a check on em_cpu_get() on the driver side shouldn't hurt. We
don't actually have upstream drivers using that API yet but I intend to
change that soon. I guess we'll need to have that discussion with each
individual CPUFreq driver maintainer but that hopefully shouldn't be a
problem.

Thanks for the feedback,
Quentin