linux-kernel - Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency invariance

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Date:   Tue, 29 Jun 2021 09:38:21 -0400
From:   Qian Cai <quic_qiancai@...cinc.com>
To:     Ionela Voinescu <ionela.voinescu@....com>
CC:     Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Mel Gorman <mgorman@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Will Deacon <will@...nel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH V3 0/4] cpufreq: cppc: Add support for frequency
 invariance

On 6/29/2021 5:06 AM, Ionela Voinescu wrote:
>> Ionela, I found that set ACPI_PROCESSOR=y instead of ACPI_PROCESSOR=m
>> will fix the previous mentioned issues here (any explanations of that?)
>> even though the scaling down is not perfect. Now, we have the following
>> on this idle system:
>>
> 
> I don't see how this would have played a role. The cppc cpufreq driver
> depends on functionality gated by CONFIG_ACPI_CPPC_LIB which in turn
> needs CONFIG_ACPI_PROCESSOR to trigger the parsing of the _CPC objects.
> If CONFIG_ACPI_PROCESSOR functionality is not built in or loaded, the
> cppc cpufreq driver could not be used at all.

Ionela, that is fine. I can live with setting ACPI_PROCESSOR=y to workaround. I
was more of just curious about why manually loading processor.ko would set the
lowest to 2GHz instead of 1GHz.

Anyway, if running below the lowest is not the a concern, then I have concluded
my testing here. Feel free to include:

Tested-by: Qian Cai <quic_qiancai@...cinc.com>