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

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Message-ID: <CAJZ5v0hWUdRdbPL2=qybaEsNfPzAqdxW+xBrjwy4HaBXnTwD0g@mail.gmail.com>
Date: Wed, 23 Apr 2025 16:26:38 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Lifeng Zheng <zhenglifeng1@...wei.com>, linux-pm@...r.kernel.org, 
	Vincent Guittot <vincent.guittot@...aro.org>, Nicholas Chin <nic.c3.14@...il.com>, 
	"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 Tue, Apr 22, 2025 at 11:54 AM Viresh Kumar <viresh.kumar@...aro.org> 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;

IIUC policy->boost_enabled is false at this point, so say that
boost_state(cpu) returns true and say cpufreq_boost_enabled() returns
false.

cpufreq_online() will see policy->boost_enabled ==
cpufreq_boost_enabled(), so it won't do anything regarding boost, and
say that this happens for all online CPUs.

cpufreq_boost_enabled() will be false, policy->boost_enabled will be
false for every policy, but boost will be effectively enabled AFAICS.

> +               }
> +       }
>
>         return result;
>
> --