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

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Message-ID: <20200922162540.GB796@arm.com>
Date:   Tue, 22 Sep 2020 17:25:40 +0100
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
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

Hi,

Sorry for the delay, I just got back from holiday as well.

On Monday 07 Sep 2020 at 11:41:54 (+0530), Viresh Kumar wrote:
> 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.
> 

Okay, I'll follow your lead and remove the per-cpu structures.

Thanks,
Ionela.

> -- 
> viresh