linux-kernel - Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support

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Date:   Fri, 7 Jul 2017 18:06:30 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Russell King - ARM Linux <linux@....linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Juri Lelli <juri.lelli@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant
 load-tracking support

On 07/07/17 17:18, Rafael J. Wysocki wrote:
> On Fri, Jul 7, 2017 at 6:01 PM, Dietmar Eggemann
> <dietmar.eggemann@....com> wrote:
>> On 06/07/17 11:40, Viresh Kumar wrote:
>>> On 06-07-17, 10:49, Dietmar Eggemann wrote:

[...]

>> So what about I call arch_set_freq_scale() in __cpufreq_notify_transition() in the
>> CPUFREQ_POSTCHANGE case for slow-switching and in cpufreq_driver_fast_switch() for
>> fast-switching?
> 
> Why don't you do this in drivers instead of in the core?
> 
> Ultimately, the driver knows what frequency it has requested, so why
> can't it call arch_set_freq_scale()?

That's correct but for arm/arm64 we have a lot of different cpufreq
drivers to deal with. And doing this call to arch_set_freq_scale() once
in the cpufreq core will cover them all.

[...]