linux-kernel - Re: [PATCH 3/3] thermal: cpu_cooling: Migrate to using the EM framework

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Date:   Wed, 10 Apr 2019 11:36:45 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     edubezval@...il.com, rui.zhang@...el.com, javi.merino@...nel.org,
        amit.kachhap@...il.com, rjw@...ysocki.net, will.deacon@....com,
        catalin.marinas@....com, daniel.lezcano@...aro.org,
        dietmar.eggemann@....com, ionela.voinescu@....com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/3] thermal: cpu_cooling: Migrate to using the EM
 framework

On Wednesday 10 Apr 2019 at 15:44:23 (+0530), Viresh Kumar wrote:
> On 10-04-19, 09:57, Quentin Perret wrote:
> > Hmm, indeed... I thought cpufreq_table_validate_and_sort() was actively
> > sorting the table but it seems I was wrong.
> > 
> > But I _think_ in practice the freq table actually happens to be sorted
> > for the upstream cpufreq drivers with the CPUFREQ_IS_COOLING_DEV flag
> > set. Most of them use dev_pm_opp_init_cpufreq_table() which guarantees
> > the table is sorted and qoriq-cpufreq explicitly sorts the table. But
> > I'm not sure about qcom-cpufreq-hw ...
> > 
> > So, if the above is true, perhaps I could simply add a check to mandate
> > that policy->freq_table_sorted != CPUFREQ_TABLE_SORTED_UNSORTED for
> > cpu_cooling ? That shouldn't harm the existing users.
> 
> Right, I think most of the platforms will have it sorted anyway right now, but
> you never know if one or two of them don't. Maybe just add the above conditional
> and put out an error or WARN or something, so people know that something broke.

Right, WARN + bail out should do it. I'll do the change in v2.

Thanks !
Quentin