linux-kernel - Re: [PATCH v7 02/23] PM: EM: Extend em_cpufreq_update

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Date: Wed, 17 Jan 2024 11:10:40 +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 02/23] PM: EM: Extend em_cpufreq_update_efficiencies()
 argument list

On 17/01/2024 09:56, Lukasz Luba wrote:
> In order to prepare the code for the modifiable EM perf_state table,
> make em_cpufreq_update_efficiencies() take a pointer to the EM table
> as its second argument and modify it to use that new argument instead
> of the 'table' member of dev->em_pd.
> 
> No functional impact.
> 
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
>   kernel/power/energy_model.c | 8 +++-----
>   1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> index 8b9dd4a39f63..42486674b834 100644
> --- a/kernel/power/energy_model.c
> +++ b/kernel/power/energy_model.c
> @@ -237,10 +237,10 @@ static int em_create_pd(struct device *dev, int nr_states,
>   	return 0;
>   }
>   
> -static void em_cpufreq_update_efficiencies(struct device *dev)
> +static void
> +em_cpufreq_update_efficiencies(struct device *dev, struct em_perf_state *table)
>   {
>   	struct em_perf_domain *pd = dev->em_pd;
> -	struct em_perf_state *table;
>   	struct cpufreq_policy *policy;
>   	int found = 0;
>   	int i;
> @@ -254,8 +254,6 @@ static void em_cpufreq_update_efficiencies(struct device *dev)
>   		return;
>   	}

NIT: It's not shown here, but in the check above this line

	if (!_is_cpu_device(dev) || !pd)

The !pd check should be removed because em_cpufreq_update_efficiencies() 
is only called after doing

	dev->em_pd->flags |= flags;

So compiler will optimize the !pd out anyway. But this is not directly 
related to the PR, so just a NIT.

>   
> -	table = pd->table;
> -
>   	for (i = 0; i < pd->nr_perf_states; i++) {
>   		if (!(table[i].flags & EM_PERF_STATE_INEFFICIENT))
>   			continue;
> @@ -397,7 +395,7 @@ int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
>   
>   	dev->em_pd->flags |= flags;
>   
> -	em_cpufreq_update_efficiencies(dev);
> +	em_cpufreq_update_efficiencies(dev, dev->em_pd->table);
>   
>   	em_debug_create_pd(dev);
>   	dev_info(dev, "EM: created perf domain\n");

Reviewed-by: Hongyan Xia <hongyan.xia2@....com>