linux-kernel - Re: [PATCH v2 2/2] [RFC] CPUFreq: Add support for cpu-perf-dependencies

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Message-ID: <20201006071909.3cgz7i5v35dgnuzn@vireshk-i7>
Date:   Tue, 6 Oct 2020 12:49:09 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Nicola Mazzucato <nicola.mazzucato@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        sudeep.holla@....com, rjw@...ysocki.net, vireshk@...nel.org,
        robh+dt@...nel.org, daniel.lezcano@...aro.org,
        morten.rasmussen@....com, chris.redpath@....com
Subject: Re: [PATCH v2 2/2] [RFC] CPUFreq: Add support for
 cpu-perf-dependencies

On 24-09-20, 10:53, Nicola Mazzucato wrote:
> I am seeking some feedback/comments on the following approach.
> 
> Intro:
> Info of performance depency for cpus will be beneficial for systems
> where f/w description of the CPU performance control domain is different
> from the clock domain, e.g. per-CPU control with multiple CPUs sharing
> clock, and kernel OSPM s/w components need to take CPU performance
> dependency into account.
> Essentially these s/w components will have to be provided with
> this information from dt and this RFC is presenting a possible way
> to do so.

I am not sure I understand what performance control mean here. Can you please
elaborate a bit more on that ? For example, with current code and understanding,
a cpufreq policy belongs to a group of CPUs which change their frequency
together, which also mean that they change their performance level together and
so I am not able to understand what's going on here. Sorry about that.

What kind of hardware configuration doesn't work with this ?

-- 
viresh