linux-kernel - Re: [PATCH v7 04/23] PM: EM: Refactor em_pd_get_efficient

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Date: Wed, 17 Jan 2024 12:45:42 +0000
From: Hongyan Xia <hongyan.xia2@....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, mhiramat@...nel.org, qyousef@...alina.io, wvw@...gle.com,
 xuewen.yan94@...il.com
Subject: Re: [PATCH v7 04/23] PM: EM: Refactor em_pd_get_efficient_state() to
 be more flexible

On 17/01/2024 09:56, Lukasz Luba wrote:
> The Energy Model (EM) is going to support runtime modification. There
> are going to be 2 EM tables which store information. This patch aims
> to prepare the code to be generic and use one of the tables. The function
> will no longer get a pointer to 'struct em_perf_domain' (the EM) but
> instead a pointer to 'struct em_perf_state' (which is one of the EM's
> tables).
> 
> Prepare em_pd_get_efficient_state() for the upcoming changes and
> make it possible to be re-used. Return an index for the best performance
> state for a given EM table. The function arguments that are introduced
> should allow to work on different performance state arrays. The caller of
> em_pd_get_efficient_state() should be able to use the index either
> on the default or the modifiable EM table.
> 
> Reviewed-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
>   include/linux/energy_model.h | 30 +++++++++++++++++-------------
>   1 file changed, 17 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
> index c19e7effe764..b01277b17946 100644
> --- a/include/linux/energy_model.h
> +++ b/include/linux/energy_model.h
> @@ -175,33 +175,35 @@ void em_dev_unregister_perf_domain(struct device *dev);
>   
>   /**
>    * em_pd_get_efficient_state() - Get an efficient performance state from the EM
> - * @pd   : Performance domain for which we want an efficient frequency
> - * @freq : Frequency to map with the EM
> + * @table:		List of performance states, in ascending order
> + * @nr_perf_states:	Number of performance states
> + * @freq:		Frequency to map with the EM
> + * @pd_flags:		Performance Domain flags
>    *
>    * It is called from the scheduler code quite frequently and as a consequence
>    * doesn't implement any check.
>    *
> - * Return: An efficient performance state, high enough to meet @freq
> + * Return: An efficient performance state id, high enough to meet @freq
>    * requirement.
>    */
> -static inline
> -struct em_perf_state *em_pd_get_efficient_state(struct em_perf_domain *pd,
> -						unsigned long freq)
> +static inline int
> +em_pd_get_efficient_state(struct em_perf_state *table, int nr_perf_states,
> +			  unsigned long freq, unsigned long pd_flags)
>   {
>   	struct em_perf_state *ps;
>   	int i;
>   
> -	for (i = 0; i < pd->nr_perf_states; i++) {
> -		ps = &pd->table[i];
> +	for (i = 0; i < nr_perf_states; i++) {
> +		ps = &table[i];
>   		if (ps->frequency >= freq) {
> -			if (pd->flags & EM_PERF_DOMAIN_SKIP_INEFFICIENCIES &&
> +			if (pd_flags & EM_PERF_DOMAIN_SKIP_INEFFICIENCIES &&
>   			    ps->flags & EM_PERF_STATE_INEFFICIENT)
>   				continue;
> -			break;
> +			return i;
>   		}
>   	}
>   
> -	return ps;
> +	return nr_perf_states - 1;
>   }
>   
>   /**
> @@ -226,7 +228,7 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
>   {
>   	unsigned long freq, ref_freq, scale_cpu;
>   	struct em_perf_state *ps;
> -	int cpu;
> +	int cpu, i;
>   
>   	if (!sum_util)
>   		return 0;
> @@ -251,7 +253,9 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
>   	 * Find the lowest performance state of the Energy Model above the
>   	 * requested frequency.
>   	 */
> -	ps = em_pd_get_efficient_state(pd, freq);
> +	i = em_pd_get_efficient_state(pd->table, pd->nr_perf_states, freq,
> +				      pd->flags);
> +	ps = &pd->table[i];
>   
>   	/*
>   	 * The capacity of a CPU in the domain at the performance state (ps)

Reviewed-by: Hongyan Xia <hongyan.xia@....com>