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

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Date:   Wed, 30 Jan 2019 15:47:15 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Quentin Perret <quentin.perret@....com>
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 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 ?

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().

-- 
viresh