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
and avoid updating the QoS request when the _PPC return value has not
changed.
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.
While at it, move the _PPC return value check against the state count
earlier to avoid setting performance_platform_limit to an invalid value.
Reported-by: Pratyush Yadav <ptyadav@xxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
drivers/acpi/processor_perflib.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 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 +74,30 @@ static int acpi_processor_get_platform_l
}
}
+ index = ppc;
+
+ if (pr->performance_platform_limit == index ||
+ ppc >= pr->performance->state_count)
+ return 0;
+
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)))
+ if (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);
