linux-kernel - Re: [PATCH 2/6] cpufreq: acpi: Re-sync CPU boost state on system resume

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Message-ID: <1b914523-5b26-4fc0-b5c5-4b2f90ffaa3d@gmail.com>
Date: Tue, 22 Apr 2025 20:57:22 -0600
From: Nicholas Chin <nic.c3.14@...il.com>
To: Viresh Kumar <viresh.kumar@...aro.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Lifeng Zheng <zhenglifeng1@...wei.com>
Cc: linux-pm@...r.kernel.org, Vincent Guittot <vincent.guittot@...aro.org>,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] cpufreq: acpi: Re-sync CPU boost state on system
 resume

On 2025-04-22 03:53, Viresh Kumar wrote:
> During suspend/resume cycles, platform firmware may alter the CPU boost
> state.
> 
> If boost is disabled before suspend, it correctly remains off after
> resume. However, if firmware re-enables boost during suspend, the system
> may resume with boost frequencies enabled—even when the boost flag was
> originally disabled. This violates expected behavior.
> 
> Ensure the boost state is re-synchronized with the kernel policy during
> system resume to maintain consistency.
> 
> Fixes: 2b16c631832d ("cpufreq: ACPI: Remove set_boost in acpi_cpufreq_cpu_init()")
> Reported-by: Nicholas Chin <nic.c3.14@...il.com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220013
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/acpi-cpufreq.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index 7002e8de8098..0ffabf740ff5 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -893,8 +893,19 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
>  	if (perf->states[0].core_frequency * 1000 != freq_table[0].frequency)
>  		pr_warn(FW_WARN "P-state 0 is not max freq\n");
>  
> -	if (acpi_cpufreq_driver.set_boost)
> -		policy->boost_supported = true;
> +	if (acpi_cpufreq_driver.set_boost) {
> +		if (policy->boost_supported) {
> +			/*
> +			 * The firmware may have altered boost state while the
> +			 * CPU was offline (for example during a suspend-resume
> +			 * cycle).
> +			 */
> +			if (policy->boost_enabled != boost_state(cpu))
> +				set_boost(policy, policy->boost_enabled);
> +		} else {
> +			policy->boost_supported = true;
> +		}
> +	}
>  
>  	return result;
>  

The first two patches in this series appear to work as intended. The boost state (both enabled and disabled) persists across a resume from S3 suspend.

Tested-by: Nicholas Chin <nic.c3.14@...il.com>