ACPI: processor: perflib: Use the "no limit" frequency QoS

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@amazon.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Pratyush Yadav <ptyadav@amazon.de>
Tested-by: Pratyush Yadav <ptyadav@amazon.de>

diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 970f04a958cd220a2b6a826374ba90fb458aaad0..0da85fc2a7e41cc55cf631a73858d959cb856344 100644 (file)
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -53,6 +53,8 @@ static int acpi_processor_get_platform_limit(struct acpi_processor *pr)
 {
        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_limit(struct acpi_processor *pr)
                }
        }
 
+       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);