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Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with "dynamic_switching"

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On Fri, Jul 14, 2017 at 9:01 AM, Dominik Brodowski
<linux@dominikbrodowski.net> wrote:
> On Thu, Jul 13, 2017 at 06:19:53PM +0200, Rafael J. Wysocki wrote:
>> On Thu, Jul 13, 2017 at 7:40 AM, Viresh Kumar <viresh.kumar@linaro.org> wrote:
>> > There is no limitation in the ondemand or conservative governors which
>> > disallow the transition_latency to be greater than 10 ms.
>> >
>> > The max_transition_latency field is rather used to disallow automatic
>> > dynamic frequency switching for platforms which didn't wanted these
>> > governors to run.
>> >
>> > Replace max_transition_latency with a boolean (dynamic_switching) and
>> > check for transition_latency == CPUFREQ_ETERNAL along with that. This
>> > makes it pretty straight forward to read/understand now.
>>
>> Well, using CPUFREQ_ETERNAL for that on the driver side is still not
>> particularly straightforward IMO, so maybe add a
>> "no_dynamic_switching" to the driver structure and set it to "true"
>> for the one driver in question?
>
> IIRC it's not just one driver which sets the latency to CPUFREQ_ETERNAL, and
> where dynamic switching might be harmful or at least lead to undefined
> behavior.

OK

Still, though, using CPUFREQ_ETERNAL to indicate the "no dynamic
switching" condition is somewhat convoluted, so why don't we have a
flag to *explicitly* say that instead?

Do you know which drivers they are or is it just all drivers that use
CPUFREQ_ETERNAL?

Thanks,
Rafael

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[RFC V2 1/6] cpufreq: Replace "max_transition_latency" with "dynamic_switching" Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-13 07:50 +0200
  Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with "dynamic_switching" "Rafael J. Wysocki" <rafael@kernel.org> - 2017-07-13 18:30 +0200
    Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with  "dynamic_switching" Dominik Brodowski <linux@dominikbrodowski.net> - 2017-07-14 09:10 +0200
      Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with "dynamic_switching" "Rafael J. Wysocki" <rafael@kernel.org> - 2017-07-14 13:20 +0200
        Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with "dynamic_switching" "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-15 00:20 +0200
          Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with  "dynamic_switching" Dominik Brodowski <linux@dominikbrodowski.net> - 2017-07-15 07:20 +0200
            Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with "dynamic_switching" "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-15 14:40 +0200
              Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with  "dynamic_switching" Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-17 14:00 +0200
                Re: [RFC V2 1/6] cpufreq: Replace "max_transition_latency" with "dynamic_switching" "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-17 14:30 +0200

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