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Subject: Re: [PATCH] sched/cpufreq: Align trace event behavior of fast
 switching
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>
References: <20190807153340.11516-1-douglas.raillard@arm.com>
 <CAJZ5v0gqqoOzjUMhUgqKzaj8tCegddJphr+MHj5HD2_VAc1QYQ@mail.gmail.com>
From:   Douglas Raillard <douglas.raillard@arm.com>
Organization: ARM
Message-ID: <433793e3-14c4-9f3b-d503-76471a98b0af@arm.com>
Date:   Thu, 8 Aug 2019 17:18:00 +0100
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Hi Rafael,

On 8/7/19 9:40 PM, Rafael J. Wysocki wrote:
> On Wed, Aug 7, 2019 at 5:34 PM Douglas RAILLARD
> <douglas.raillard@arm.com> wrote:
>>
>> Fast switching path only emits an event for the CPU of interest, whereas the
>> regular path emits an event for all the CPUs that had their frequency changed,
>> i.e. all the CPUs sharing the same policy.
>>
>> With the current behavior, looking at cpu_frequency event for a given CPU that
>> is using the fast switching path will not give the correct frequency signal.
> 
> Do you actually have any systems where that is a problem?  If so, then
> what are they?
> 

That happens on Google Pixel 3 smartphone, which uses this cpufreq driver: drivers/cpufreq/qcom-cpufreq-hw.c.

[1] git clone https://git.linaro.org/people/amit.pundir/linux.git -b blueline-mainline-tracking

Thanks,
Douglas