linux-kernel - Re: [PATCH 02/17] PM: EM: Find first CPU online while updating OPP efficiency

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Message-ID: <c35741e3-f0c9-bec4-7e9a-c96e5949839f@arm.com>
Date:   Tue, 11 Apr 2023 17:40:47 +0200
From:   Pierre Gondois <pierre.gondois@....com>
To:     Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, rafael@...nel.org
Cc:     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, ionela.voinescu@....com,
        rostedt@...dmis.org, mhiramat@...nel.org
Subject: Re: [PATCH 02/17] PM: EM: Find first CPU online while updating OPP
 efficiency

Hello Lukasz,

On 3/14/23 11:33, Lukasz Luba 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 265d51a948d4..3d8d1fad00ac 100644
> --- a/kernel/power/energy_model.c
> +++ b/kernel/power/energy_model.c
> @@ -246,12 +246,19 @@ 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;

Since dev is a CPU, I think it shouldn be possible to get the cpu id via 'dev->id'.
If so the code below should not be necessary anymore.

>   
> -	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);
> +	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");
>   		return;

Regards,
Pierre