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

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Message-ID: <20190130102042.uwxpsep5vmeq4h62@queper01-lin>
Date:   Wed, 30 Jan 2019 10:20:45 +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 Wednesday 30 Jan 2019 at 15:47:15 (+0530), Viresh Kumar wrote:
> On 30-01-19, 09:12, Quentin Perret wrote:
> > What I had in mind is something as simple as:
> > 
> > 	void of_dev_pm_opp_register_em(struct cpumask *cpus)
> > 	{
> > 		/* Bail out if an EM is there */
> > 		if (em_cpu_get(cpumask_first(cpus)))
> > 			return;
> > 
> > 		/* Check prerequisites: dpc coeff in DT, ... */
> > 		...
> > 
> > 		em_register_perf_domain(...);
> > 	}
> > 
> > IIUC, Matthias' point was that if the EM is already registered, there is
> > no good reason to call em_register_perf_domain() again. Now, that should
> > in fact be harmless because em_register_perf_domain() already does that
> > check. It's just cleaner and easier to understand from a conceptual
> > standpoint to not call that function several times for no reason I
> > assume.
> 
> If there is no good reason to call em_register_perf_domain() several
> times, then the same applies to of_dev_pm_opp_register_em() as well,
> isn't it ?

Hrmpf, that is true ... :-)

> This is init code anyway isn't going to run a lot, so I wouldn't
> suggest adding any such (duplicate) checks in
> of_dev_pm_opp_register_em().

Fair enough, I'll post a v2 w/o the check and we'll see if others have
complaints.

Thanks,
Quentin