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

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Message-ID: <20201106092442.v5fao2dyl3lemwyh@vireshk-i7>
Date:   Fri, 6 Nov 2020 14:54:42 +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,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        sudeep.holla@....com, rjw@...ysocki.net, vireshk@...nel.org,
        robh+dt@...nel.org, sboyd@...nel.org, nm@...com,
        daniel.lezcano@...aro.org, morten.rasmussen@....com,
        chris.redpath@....com
Subject: Re: [PATCH v3 3/3] [RFC] CPUFreq: Add support for
 cpu-perf-dependencies

On 02-11-20, 12:01, Nicola Mazzucato wrote:
> Hi All,
> 
> This is a continuation of the previous v2, where we focused mostly on the
> dt binding.
> 
> I am seeking some feedback/comments on the following two approaches.
> 
> Intro:
> We have seen that in a system where performance control and hardware
> description do not match (i.e. per-cpu), we still need the information of
> how the v/f lines are shared among the cpus. We call this information
> "performance dependencies".
> We got this info through the opp-shared (the previous 2 patches aim for
> that).
> 
> Problem:
> How do we share such info (retrieved from a cpufreq driver) to other
> consumers that rely on it? I have two proposals.

FWIW, we already have a case in kernel where something similar is
done.

commit f4fd3797848a ("acpi-cpufreq: Add new sysfs attribute freqdomain_cpus")

and the information is shared via:

/sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus

-- 
viresh