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

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Date:   Mon, 21 Jun 2021 16:48:44 -0400
From:   Qian Cai <quic_qiancai@...cinc.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Ionela Voinescu <ionela.voinescu@....com>,
        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>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Will Deacon <will@...nel.org>
CC:     <linux-pm@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
        <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 6/21/2021 5:19 AM, Viresh Kumar wrote:
> CPPC cpufreq driver is used for ARM servers and this patch series tries to
> provide counter-based frequency invariance support for them in the absence for
> architecture specific counters (like AMUs).

Viresh, this series works fine on my quick tests so far. BTW, I noticed some strange things even with the series applied mentioned below when reading acpi_cppc vs cpufreq sysfs. Do you happen to know are those just hardware/firmware issues because Linux just faithfully exported the register values?

== Arm64 server Foo ==
CPU max MHz:                     3000.0000
CPU min MHz:                     1000.0000

/sys/devices/system/cpu/cpu0/acpi_cppc/highest_perf
300
/sys/devices/system/cpu/cpu0/acpi_cppc/lowest_freq
1000
/sys/devices/system/cpu/cpu0/acpi_cppc/lowest_nonlinear_perf
200
/sys/devices/system/cpu/cpu0/acpi_cppc/lowest_perf
100
/sys/devices/system/cpu/cpu0/acpi_cppc/nominal_freq <--- should be 3000?
2800
/sys/devices/system/cpu/cpu0/acpi_cppc/nominal_perf <--- should be 300?
280
/sys/devices/system/cpu/cpu0/acpi_cppc/reference_perf
100

== Arm64 server Bar ==
CPU max MHz:                     3000.0000
CPU min MHz:                     375.0000

/sys/devices/system/cpu/cpu0/acpi_cppc/highest_perf <--- should be 3000? There is no cpufreq boost.
3300
/sys/devices/system/cpu/cpu0/acpi_cppc/lowest_freq <--- don't understand why 0.
0
/sys/devices/system/cpu/cpu0/acpi_cppc/lowest_nonlinear_perf
375
/sys/devices/system/cpu/cpu0/acpi_cppc/lowest_perf
375
/sys/devices/system/cpu/cpu0/acpi_cppc/nominal_freq <--- ditto
0
/sys/devices/system/cpu/cpu0/acpi_cppc/nominal_perf
3000
/sys/devices/system/cpu/cpu0/acpi_cppc/reference_perf
100