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

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Date:   Mon, 23 Oct 2023 19:06:05 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
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,
        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 Lukasz,

On 25/09/2023 10:11, 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.

I'm failing to do the connection with the description and the change.

Perhaps, the changelog shall explain why 'cpu' must be replaced with the 
first active cpu ?

> 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);
> +	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;

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