linux-kernel - Re: [PATCH] cpufreq,cppc: fix issue when hotplugging out policy->cpu

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Message-ID: <20200907061154.iiyaq4m3vjtrlkp4@vireshk-i7>
Date:   Mon, 7 Sep 2020 11:41:54 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     rjw@...ysocki.net, sudeep.holla@....com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq,cppc: fix issue when hotplugging out policy->cpu

On 04-09-20, 10:43, Ionela Voinescu wrote:
> Do you know why it was designed this way in the first place?

No.

> I assumed it was designed like this (per-cpu cppc_cpudata structures) to
> allow for the future addition of support for the HW_ALL CPPC coordination
> type. In that case you can still have PSD (dependency) domains but the
> desired performance controls would be per-cpu, with the coordination
> done in hardware/firmware. So, in the HW_ALL case you'd end up having
> different performance controls even for CPUs in the same policy.
> Currently the CPPC driver only supports SW_ANY which is the traditional
> cpufreq approach.

Then the person who would add that feature will take care of fixing the issues
then. We should make sure we handle the current use-case optimally. And a
per-cpu thing isn't working well for that.

-- 
viresh