linux-kernel - Re: [PATCH V3 8/9] cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC

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Message-ID: <20170719163054.GA32233@light.dominikbrodowski.net>
Date:   Wed, 19 Jul 2017 18:30:54 +0200
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH V3 8/9] cpufreq: Add CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING
 cpufreq driver flag


On Wed, Jul 19, 2017 at 03:42:48PM +0530, Viresh Kumar wrote:
> The policy->transition_latency field is used for multiple purposes
> today and its not straight forward at all. This is how it is used:
> 
> A. Set the correct transition_latency value.
> 
> B. Set it to CPUFREQ_ETERNAL because:
>    1. We don't want automatic dynamic switching (with
>       ondemand/conservative) to happen at all.
>    2. We don't know the transition latency.
> 
> This patch handles the B.1. case in a more readable way. A new flag for
> the cpufreq drivers is added to disallow use of cpufreq governors which
> have dynamic_switching flag set.
> 
> All the current cpufreq drivers which are setting transition_latency
> unconditionally to CPUFREQ_ETERNAL are updated to use it. They don't
> need to set transition_latency anymore.
> 
> There shouldn't be any functional change after this patch.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>

Looks good to me, so feel free to add:

	Reviewed-by: Dominik Brodowski <linux@...inikbrodowski.net>

Best,
	Dominik

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