6.15-stable review patch. If anyone has any objections, please let me know.
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From: Jiayi Li lijiayi@kylinos.cn
commit d33bd88ac0ebb49e7f7c8f29a8c7ee9eae85d765 upstream.
If the BIOS sets a _PPC frequency limit upfront, it will fail to take effect due to a call ordering issue. Namely, freq_qos_update_request() is called before freq_qos_add_request() for the given request causing the constraint update to be ignored. The call sequence in question is as follows:
cpufreq_policy_online() acpi_cpufreq_cpu_init() acpi_processor_register_performance() acpi_processor_get_performance_info() acpi_processor_get_platform_limit() freq_qos_update_request(&perflib_req) <- inactive QoS request blocking_notifier_call_chain(&cpufreq_policy_notifier_list, CPUFREQ_CREATE_POLICY) acpi_processor_notifier() acpi_processor_ppc_init() freq_qos_add_request(&perflib_req) <- QoS request activation
Address this by adding an acpi_processor_get_platform_limit() call to acpi_processor_ppc_init(), after the perflib_req activation via freq_qos_add_request(), which causes the initial _PPC limit to be picked up as appropriate. However, also ensure that the _PPC limit will not be picked up in the cases when the cpufreq driver does not call acpi_processor_register_performance() by adding a pr->performance check to the related_cpus loop in acpi_processor_ppc_init().
Fixes: d15ce412737a ("ACPI: cpufreq: Switch to QoS requests instead of cpufreq notifier") Signed-off-by: Jiayi Li lijiayi@kylinos.cn Link: https://patch.msgid.link/20250721032606.3459369-1-lijiayi@kylinos.cn [ rjw: Consolidate pr-related checks in acpi_processor_ppc_init() ] [ rjw: Subject and changelog adjustments ] Cc: 5.4+ stable@vger.kernel.org # 5.4+: 2d8b39a62a5d ACPI: processor: Avoid NULL pointer dereferences at init time Cc: 5.4+ stable@vger.kernel.org # 5.4+: 3000ce3c52f8 cpufreq: Use per-policy frequency QoS Cc: 5.4+ stable@vger.kernel.org # 5.4+: a1bb46c36ce3 ACPI: processor: Add QoS requests for all CPUs Cc: 5.4+ stable@vger.kernel.org # 5.4+ Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/acpi/processor_perflib.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
--- a/drivers/acpi/processor_perflib.c +++ b/drivers/acpi/processor_perflib.c @@ -172,11 +172,14 @@ void acpi_processor_ppc_init(struct cpuf { 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;
- if (!pr) + if (!pr || !pr->performance) continue;
/* @@ -192,6 +195,11 @@ void acpi_processor_ppc_init(struct cpuf 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); } }