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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2022-12-28 22:24:10 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2022-12-30 19:10:02 +0100
commit99387b016022c29234c4ebf9abd34358c6e56532 (patch)
tree684dc0cf43311e196bd2b08b6a5487c55fe3ad3f
parentc02d5feb6e2f60affc6ba8606d8d614c071e2ba6 (diff)
downloadlwn-99387b016022c29234c4ebf9abd34358c6e56532.tar.gz
lwn-99387b016022c29234c4ebf9abd34358c6e56532.zip
ACPI: processor: perflib: Avoid updating frequency QoS unnecessarily
Modify acpi_processor_get_platform_limit() to avoid updating its frequency QoS request when the _PPC return value has not changed by comparing that value to the previous _PPC return value stored in the performance_platform_limit field of the struct acpi_processor corresponding to the given CPU. While at it, do the _PPC return value check against the state count earlier, to avoid setting performance_platform_limit to an invalid value, and make acpi_processor_ppc_init() use FREQ_QOS_MAX_DEFAULT_VALUE as the "no limit" frequency QoS for consistency. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
-rw-r--r--drivers/acpi/processor_perflib.c18
1 files changed, 14 insertions, 4 deletions
diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 0da85fc2a7e4..4265814c74f8 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -76,13 +76,16 @@ static int acpi_processor_get_platform_limit(struct acpi_processor *pr)
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,
index, index ? "is" : "is not");
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;
/*
@@ -178,9 +181,16 @@ void acpi_processor_ppc_init(struct cpufreq_policy *policy)
if (!pr)
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
+ * below.
+ */
+ pr->performance_platform_limit = 0;
+
ret = freq_qos_add_request(&policy->constraints,
- &pr->perflib_req,
- FREQ_QOS_MAX, INT_MAX);
+ &pr->perflib_req, FREQ_QOS_MAX,
+ FREQ_QOS_MAX_DEFAULT_VALUE);
if (ret < 0)
pr_err("Failed to add freq constraint for CPU%d (%d)\n",
cpu, ret);