linux-kernel - Re: [PATCH V2 9/9] cpufreq: scmi: Use .register

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Date:   Wed, 11 Aug 2021 15:09:13 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Quentin Perret <qperret@...gle.com>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Sudeep Holla <sudeep.holla@....com>,
        Cristian Marussi <cristian.marussi@....com>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 9/9] cpufreq: scmi: Use .register_em() callback



On 8/11/21 2:17 PM, Quentin Perret wrote:
> On Wednesday 11 Aug 2021 at 17:28:47 (+0530), Viresh Kumar wrote:
>> Set the newly added .register_em() callback to register with the EM
>> after the cpufreq policy is properly initialized.
>>
>> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
>> ---
>>   drivers/cpufreq/scmi-cpufreq.c | 55 ++++++++++++++++++++--------------
>>   1 file changed, 32 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c
>> index 75f818d04b48..b916c9e22921 100644
>> --- a/drivers/cpufreq/scmi-cpufreq.c
>> +++ b/drivers/cpufreq/scmi-cpufreq.c
>> @@ -22,7 +22,9 @@
>>   
>>   struct scmi_data {
>>   	int domain_id;
>> +	int nr_opp;
>>   	struct device *cpu_dev;
>> +	cpumask_var_t opp_shared_cpus;
> 
> Can we use policy->related_cpus and friends directly in the callback

Unfortunately not. This tricky setup code was introduced because we may
have a platform with per-CPU policy, so single bit set in
policy->related_cpus, but we want EAS to be still working on set
of CPUs. That's why we construct temporary cpumask and pass it to EM.

> instead? That should simplify the patch a bit.
> 
> Also, we can probably afford calling dev_pm_opp_get_opp_count() from the
> em_register callback as it is not a hot path, which would avoid wasting
> some 'resident' memory here that is only used during init.
> 
> Thanks,
> Quentin
>