linux-kernel - Re: sched-freq locking

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Message-ID: <56A036C2.4090403@linaro.org>
Date:	Wed, 20 Jan 2016 17:39:14 -0800
From:	Steve Muckle <steve.muckle@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Michael Turquette <mturquette@...libre.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Juri Lelli <Juri.Lelli@....com>,
	Patrick Bellasi <patrick.bellasi@....com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: sched-freq locking

On 01/20/2016 05:22 PM, Rafael J. Wysocki wrote:
> One comment here (which may be a bit off in which case please ignore it).
> 
> You seem to be thinking that sched-freq needs to be a cpufreq governor
> and thus be handled in the same way as ondemand, for example.

That's true, I hadn't really given much thought to the alternative you
mention below.

> 
> However, this doesn't have to be the case in principle.  For example,
> if we have a special driver callback specifically to work with sched-freq,
> it may just use that callback and bypass (almost) all of the usual
> cpufreq mechanics.  This way you may avoid worrying about the governor
> locking and related ugliness entirely.

That sounds good but I'm worried about other consequences of taking
cpufreq out of the loop. For example wouldn't we need a new way for
something like thermal to set frequency limits?

thanks,
steve