linux-kernel - Re: [PATCH v3] cpufreq/cppc: Remove the desired

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Message-ID: <20240606090737.z3qenphikjs5ijj4@vireshk-i7>
Date: Thu, 6 Jun 2024 14:37:37 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Riwen Lu <luriwen@...mail.com>, beata.michalska@....com,
	ionela.voinescu@....com
Cc: rafael@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, hotran@....com,
	Riwen Lu <luriwen@...inos.cn>
Subject: Re: [PATCH v3] cpufreq/cppc: Remove the desired_perf compare when
 set target

Ionela, Beata,

On 30-05-24, 19:08, Riwen Lu wrote:
> From: Riwen Lu <luriwen@...inos.cn>
> 
> There is a case that desired_perf is exactly the same with the old perf,
> but the actual current freq is not.
> 
> This happened in S3 while the cpufreq governor is set to powersave.
> During cpufreq resume process, the booting CPU's new_freq obtained via
> .get() is the highest frequency, while the policy->cur and
> cpu->perf_ctrls.desired_perf are in the lowest level(powersave
> governor). Causing the warning: "CPU frequency out of sync:", and set
> policy->cur to new_freq. Then the governor->limits() calls
> cppc_cpufreq_set_target() to configures the CPU frequency and returns
> directly because the desired_perf converted from target_freq is the
> same with cpu->perf_ctrls.desired_perf and both are the lowest_perf.
> Since target_freq and policy->cur have been compared in
> __cpufreq_driver_target(), there's no need to compare desired_perf
> and cpu->perf_ctrls.desired_perf again in cppc_cpufreq_set_target()
> to ensure that the CPU frequency is properly configured.
> 
> Signed-off-by: Riwen Lu <luriwen@...inos.cn>
> 
> ---
> v1 -> v2:
>  - Update commit message and email.
> v2 -> v3:
>  - Update patch subject and commit message.
>  - Remove the desired_perf compare logic.
> ---
>  drivers/cpufreq/cppc_cpufreq.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 15f1d41920a3..337cece61ab5 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -295,9 +295,6 @@ static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,
>  	int ret = 0;
>  
>  	desired_perf = cppc_khz_to_perf(&cpu_data->perf_caps, target_freq);
> -	/* Return if it is exactly the same perf */
> -	if (desired_perf == cpu_data->perf_ctrls.desired_perf)
> -		return ret;
>  
>  	cpu_data->perf_ctrls.desired_perf = desired_perf;
>  	freqs.old = policy->cur;

Any objections to this change ?

-- 
viresh