linux-kernel - Re: [PATCH 1/8] cpufreq: Auto-register with energy model if asked

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Message-ID: <821da524-0ca5-6923-2f57-2d6ed4723c7d@arm.com>
Date:   Tue, 10 Aug 2021 16:33:33 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Vincent Donnefort <vincent.donnefort@....com>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] cpufreq: Auto-register with energy model if asked

On 8/10/21 10:38 AM, Viresh Kumar wrote:
> On 10-08-21, 10:36, Lukasz Luba wrote:
>> The of_cpufreq_cooling_register() should be called after the EM
>> is present for the CPU device. When you check that function,
>> you will see that we call
>> em_cpu_get(policy->cpu)
>> to get the EM pointer. Otherwise IPA might fail.
> 
> Good point.
> 

In other patch set I had a discussion with Quentin and I've checked
the Performance Domains setup code. There is a code triggering the
rebuilding perf domains with EM from governor. We cannot call
EM registration so late in this cpufreq_online(), not after
cpufreq_init_policy() call.

So this dev_pm_opp_of_unregister_em() must be called before
the policy is initialized. I'm not sure if you still would like
to push forward this patch set in this case.