Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency"

From	"Rafael J. Wysocki" <rafael@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency"
Date	2016-07-23 01:50 +0200
Message-ID	<rXSmB-3XA-7@gated-at.bofh.it> (permalink)
References	<rXKp3-7uV-7@gated-at.bofh.it> <rXQb7-2Jh-1@gated-at.bofh.it> <rXQb7-2Jh-9@gated-at.bofh.it> <rXQuu-2Qh-17@gated-at.bofh.it> <rXScV-3Uh-19@gated-at.bofh.it>
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On Sat, Jul 23, 2016 at 1:30 AM, Viresh Kumar <viresh.kumar@linaro.org> wrote:
> On 22-07-16, 23:46, Rafael J. Wysocki wrote:
>> On Friday, July 22, 2016 02:28:52 PM Viresh Kumar wrote:
>> > On 22-07-16, 23:31, Rafael J. Wysocki wrote:
>> > > > cpufreq.c
>> > > >
>> > > >         if (policy->governor->max_transition_latency &&
>> > > >             policy->cpuinfo.transition_latency >
>> > > >             policy->governor->max_transition_latency) {
>> > > >
>> > > > - And this check will always fail, unless max_transition_latency is zero.
>> > >
>> > > Why would it fail?  If governor->max_transition_latency is non-zero, but less
>> > > than UNIT_MAX, the condition checked will be true to my eyes.
>> >
>> > Bad wording. Sorry.
>> >
>> > I meant, this 'if' check will always succeed (as you also noted), and
>> > so we will always get the error message reported in this patch.
>>
>> Not always, but for drivers setting cpuinfo.transition_latency to CPUFREQ_ETERNAL.
>
> So the drivers which have set their transition_latency to
> CPUFREQ_ETERNAL, can't use ondemand governor unless
> governor->max_transition_latency is set to 0 from userspace.
>
> What should be done about this patch then ? It broke in late 2015.

I'll apply the revert with a "Cc: stable" tag.

Question is what to do about the other drivers setting
cpuinfo.transition_latency to CPUFREQ_ETERNAL.

Thanks,
Rafael

Thread

[PATCH] Revert "cpufreq: pcc-cpufreq: update default value of  cpuinfo_transition_latency" Andreas Herrmann <aherrmann@suse.com> - 2016-07-22 17:20 +0200
  Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of  cpuinfo_transition_latency" Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-22 17:40 +0200
    Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency" "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-22 23:30 +0200
      Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of  cpuinfo_transition_latency" Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-22 23:30 +0200
        Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency" "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-22 23:50 +0200
          Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of  cpuinfo_transition_latency" Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-23 01:40 +0200
            Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency" "Rafael J. Wysocki" <rafael@kernel.org> - 2016-07-23 01:50 +0200
              Re: [PATCH] Revert "cpufreq: pcc-cpufreq: update default value of  cpuinfo_transition_latency" Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-23 02:00 +0200

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