linux-kernel - Re: [PATCH v4 03/18] PM: EM: Find first CPU online while updating OPP efficiency

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Message-ID: <8a9a0d27-b714-a884-ae32-728cde21dddd@arm.com>
Date:   Fri, 29 Sep 2023 09:32:09 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dietmar.eggemann@....com, rui.zhang@...el.com,
        amit.kucheria@...durent.com, amit.kachhap@...il.com,
        daniel.lezcano@...aro.org, viresh.kumar@...aro.org,
        len.brown@...el.com, pavel@....cz, mhiramat@...nel.org,
        qyousef@...alina.io, wvw@...gle.com
Subject: Re: [PATCH v4 03/18] PM: EM: Find first CPU online while updating OPP
 efficiency

Hi Rafael,

Thank you having reviewing those patches!

On 9/26/23 19:32, Rafael J. Wysocki wrote:
> On Mon, Sep 25, 2023 at 10:11 AM Lukasz Luba <lukasz.luba@....com> wrote:
>>
>> The Energy Model might be updated at runtime and the energy efficiency
>> for each OPP may change. Thus, there is a need to update also the
>> cpufreq framework and make it aligned to the new values. In order to
>> do that, use a first online CPU from the Performance Domain.
>>
>> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
>> ---
>>   kernel/power/energy_model.c | 11 +++++++++--
>>   1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
>> index 42486674b834..3dafdd7731c4 100644
>> --- a/kernel/power/energy_model.c
>> +++ b/kernel/power/energy_model.c
>> @@ -243,12 +243,19 @@ em_cpufreq_update_efficiencies(struct device *dev, struct em_perf_state *table)
>>          struct em_perf_domain *pd = dev->em_pd;
>>          struct cpufreq_policy *policy;
>>          int found = 0;
>> -       int i;
>> +       int i, cpu;
>>
>>          if (!_is_cpu_device(dev) || !pd)
>>                  return;
>>
>> -       policy = cpufreq_cpu_get(cpumask_first(em_span_cpus(pd)));
>> +       /* Try to get a CPU which is online and in this PD */
>> +       cpu = cpumask_first_and(em_span_cpus(pd), cpu_active_mask);
> 
> The comment talks about "online" and cpu_active_mask is used.  Isn't
> it a bit inconsistent?

good point, I'll change the word to 'active'

> 
>> +       if (cpu >= nr_cpu_ids) {
>> +               dev_warn(dev, "EM: No online CPU for CPUFreq policy\n");
>> +               return;
>> +       }
>> +
>> +       policy = cpufreq_cpu_get(cpu);
>>          if (!policy) {
>>                  dev_warn(dev, "EM: Access to CPUFreq policy failed\n");
>>                  return;
>> --
>> 2.25.1
>>