linux-kernel - Re: [RESEND][PATCH 2/8] PM: EM: Add artificial EM flag

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Date:   Mon, 4 Apr 2022 17:01:16 +0100
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, dietmar.eggemann@....com,
        Pierre.Gondois@....com, viresh.kumar@...aro.org, rafael@...nel.org,
        daniel.lezcano@...aro.org, linux-pm@...r.kernel.org,
        mka@...omium.org, nm@...com, sboyd@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, cristian.marussi@....com,
        sudeep.holla@....com, matthias.bgg@...il.com
Subject: Re: [RESEND][PATCH 2/8] PM: EM: Add artificial EM flag

On Monday 21 Mar 2022 at 09:57:23 (+0000), Lukasz Luba wrote:
> From: Pierre Gondois <Pierre.Gondois@....com>
> 
> The Energy Model (EM) can be used on platforms which are missing real
> power information. Those platforms would implement .get_cost() which
> populates needed values for the Energy Aware Scheduler (EAS). The EAS
> doesn't use 'power' fields from EM, but other frameworks might use them.
> Thus, to avoid miss-usage of this specific type of EM, introduce a new
> flags which can be checked by other frameworks.
> 
> Signed-off-by: Pierre Gondois <Pierre.Gondois@....com>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
>  include/linux/energy_model.h | 5 +++++
>  kernel/power/energy_model.c  | 2 ++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
> index 0a3a5663177b..92e82a322859 100644
> --- a/include/linux/energy_model.h
> +++ b/include/linux/energy_model.h
> @@ -67,11 +67,16 @@ struct em_perf_domain {
>   *
>   *  EM_PERF_DOMAIN_SKIP_INEFFICIENCIES: Skip inefficient states when estimating
>   *  energy consumption.
> + *
> + *  EM_PERF_DOMAIN_ARTIFICIAL: The power values are artificial and might be
> + *  created by platform missing real power information
>   */
>  #define EM_PERF_DOMAIN_MILLIWATTS BIT(0)
>  #define EM_PERF_DOMAIN_SKIP_INEFFICIENCIES BIT(1)
> +#define EM_PERF_DOMAIN_ARTIFICIAL BIT(2)
>  
>  #define em_span_cpus(em) (to_cpumask((em)->cpus))
> +#define em_is_artificial(em) ((em)->flags & EM_PERF_DOMAIN_ARTIFICIAL)
>  
>  #ifdef CONFIG_ENERGY_MODEL
>  #define EM_MAX_POWER 0xFFFF
> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> index 0153b0ca7b23..6ecee99af842 100644
> --- a/kernel/power/energy_model.c
> +++ b/kernel/power/energy_model.c
> @@ -384,6 +384,8 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
>  
>  	if (milliwatts)
>  		dev->em_pd->flags |= EM_PERF_DOMAIN_MILLIWATTS;
> +	else if (cb->get_cost)
> +		dev->em_pd->flags |= EM_PERF_DOMAIN_ARTIFICIAL;
>  
>  	em_cpufreq_update_efficiencies(dev);
>  

Reviewed-by: Ionela Voinescu <ionela.voinescu@....com>

> -- 
> 2.17.1
>