linux-kernel - Re: [PATCH 0/8] cpufreq: Auto-register with energy model

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Date:   Tue, 10 Aug 2021 14:53:18 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Vincent Donnefort <vincent.donnefort@....com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Cristian Marussi <cristian.marussi@....com>,
        Fabio Estevam <festevam@...il.com>,
        Kevin Hilman <khilman@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH 0/8] cpufreq: Auto-register with energy model

On Tuesday 10 Aug 2021 at 14:25:15 (+0100), Lukasz Luba wrote:
> The way I see this is that the flag in cpufreq avoids
> mistakes potentially made by driver developer. It will automaticaly
> register the *simple* EM model via dev_pm_opp_of_register_em() on behalf
> of drivers (which is already done manually by drivers). The developer
> would just set the flag similarly to CPUFREQ_IS_COOLING_DEV and be sure
> it will register at the right time. Well tested flag approach should be
> safer, easier to understand, maintain.

I would agree with all that if calling dev_pm_opp_of_register_em() was
complicated, but that is not really the case. I don't think we ever call
PM_OPP directly from cpufreq core ATM, which makes a lot of sense if you
consider PM_OPP arch-specific. I could understand that we might accept a
little 'violation' of the abstraction with this series if there were
real benefits, but I just don't see them.