From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> When _PPC returns 0, it means that the CPU frequency is not limited by the platform firmware, so make acpi_processor_get_platform_limit() update the frequency QoS request used by it to "no limit" in that case. This addresses a problem with limiting CPU frequency artificially on some systems after CPU offline/online to the frequency that corresponds to the first entry in the _PSS return package. Reported-by: Pratyush Yadav <ptyadav@xxxxxxxxx> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> --- v1 -> v2: * Move some changes into a separate patch * Update the changelog accordingly --- drivers/acpi/processor_perflib.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) Index: linux-pm/drivers/acpi/processor_perflib.c =================================================================== --- linux-pm.orig/drivers/acpi/processor_perflib.c +++ linux-pm/drivers/acpi/processor_perflib.c @@ -53,6 +53,8 @@ static int acpi_processor_get_platform_l { acpi_status status = 0; unsigned long long ppc = 0; + s32 qos_value; + int index; int ret; if (!pr) @@ -72,17 +74,27 @@ static int acpi_processor_get_platform_l } } + index = ppc; + pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr->id, - (int)ppc, ppc ? "" : "not"); + index, index ? "is" : "is not"); - pr->performance_platform_limit = (int)ppc; + pr->performance_platform_limit = index; if (ppc >= pr->performance->state_count || unlikely(!freq_qos_request_active(&pr->perflib_req))) return 0; - ret = freq_qos_update_request(&pr->perflib_req, - pr->performance->states[ppc].core_frequency * 1000); + /* + * If _PPC returns 0, it means that all of the available states can be + * used ("no limit"). + */ + if (index == 0) + qos_value = FREQ_QOS_MAX_DEFAULT_VALUE; + else + qos_value = pr->performance->states[index].core_frequency * 1000; + + ret = freq_qos_update_request(&pr->perflib_req, qos_value); if (ret < 0) { pr_warn("Failed to update perflib freq constraint: CPU%d (%d)\n", pr->id, ret);