On Mon, Jul 21, 2025 at 5:26 AM Jiayi Li <lijiayi@xxxxxxxxxx> wrote:
>
> This patch fixes an issue where _PPC frequency limits set by the BIOS
> failed to take effect due to incorrect call ordering. Previously,
> freq_qos_update_request() was being called before freq_qos_add_request(),
> causing the constraint updates to be ignored. With this fix, the frequency
> limits are now properly enforced as intended.
> The original initialization sequence was:
>
> cpufreq_policy_online()
> acpi_cpufreq_cpu_init()
> acpi_processor_get_platform_limit()
> freq_qos_update_request(&perflib_req)
> blocking_notifier_call_chain(...)
> acpi_processor_ppc_init()
> freq_qos_add_request(&perflib_req)
>
> The new sequence explicitly ensures:
>
> cpufreq_policy_online()
> acpi_cpufreq_cpu_init()
> acpi_processor_get_platform_limit()
> freq_qos_update_request(&perflib_req)
> blocking_notifier_call_chain(...)
> acpi_processor_ppc_init()
> freq_qos_add_request(&perflib_req)
> + acpi_processor_get_platform_limit()
> + freq_qos_update_request(&perflib_req)
>
> The critical change adds an immediate platform limit update after the
> QoS request is registered. This guarantees that the initial P-state
> constraint is applied before any subsequent updates, resolving the window
> where constraints could be applied out-of-order.
>
> Fixes: d15ce412737a ("ACPI: cpufreq: Switch to QoS requests instead of cpufreq notifier")
> Signed-off-by: Jiayi Li <lijiayi@xxxxxxxxxx>
> ---
> v1 -> v2:
> - Modify the commit.
> - Add pr->performance check in acpi_processor_ppc_init loop.
> ---
> ---
> drivers/acpi/processor_perflib.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
> index 64b8d1e19594..56f2b8354d62 100644
> --- a/drivers/acpi/processor_perflib.c
> +++ b/drivers/acpi/processor_perflib.c
> @@ -173,6 +173,9 @@ void acpi_processor_ppc_init(struct cpufreq_policy *policy)
> {
> unsigned int cpu;
>
> + if (ignore_ppc == 1)
> + return;
> +
> for_each_cpu(cpu, policy->related_cpus) {
> struct acpi_processor *pr = per_cpu(processors, cpu);
> int ret;
> @@ -180,6 +183,9 @@ void acpi_processor_ppc_init(struct cpufreq_policy *policy)
> if (!pr)
> continue;
>
> + if (!pr->performance)
> + continue;
> +
> /*
> * Reset performance_platform_limit in case there is a stale
> * value in it, so as to make it match the "no limit" QoS value
Applied, but I have consolidated the pr and pr->performance checks above.
I have also made some changes in the subject and changelog.
Thanks!
> @@ -193,6 +199,11 @@ void acpi_processor_ppc_init(struct cpufreq_policy *policy)
> if (ret < 0)
> pr_err("Failed to add freq constraint for CPU%d (%d)\n",
> cpu, ret);
> +
> + ret = acpi_processor_get_platform_limit(pr);
> + if (ret)
> + pr_err("Failed to update freq constraint for CPU%d (%d)\n",
> + cpu, ret);
> }
> }
>
> --
