linux-kernel - Re: [PATCH v3 3/3] [RFC] CPUFreq: Add support for cpu-perf-dependencies

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Date:   Wed, 18 Nov 2020 10:12:44 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Nicola Mazzucato <nicola.mazzucato@....com>,
        Lukasz Luba <lukasz.luba@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <vireshk@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Chris Redpath <chris.redpath@....com>
Subject: Re: [PATCH v3 3/3] [RFC] CPUFreq: Add support for
 cpu-perf-dependencies

On 17-11-20, 14:06, Rafael J. Wysocki wrote:
> Is this really a cpufreq thing, though, or is it arch stuff?  I think
> the latter, because it is not necessary for anything in cpufreq.
> 
> Yes, acpi-cpufreq happens to know this information, because it uses
> processor_perflib, but the latter may as well be used by the arch
> enumeration of CPUs and the freqdomain_cpus mask may be populated from
> there.
> 
> As far as cpufreq is concerned, if the interface to the hardware is
> per-CPU, there is one CPU per policy and cpufreq has no business
> knowing anything about the underlying hardware coordination.

It won't be used by cpufreq for now at least and yes I understand your
concern. I opted for this because we already have a cpufreq
implementation for the same thing and it is usually better to reuse
this kind of stuff instead of inventing it over.

-- 
viresh