From c02d5feb6e2f60affc6ba8606d8d614c071e2ba6 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Wed, 28 Dec 2022 22:21:49 +0100
Subject: [PATCH] ACPI: processor: perflib: Use the "no limit" frequency QoS
Git-commit: c02d5feb6e2f60affc6ba8606d8d614c071e2ba6
Patch-mainline: v6.3-rc1
References: git-fixes

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/acpi/processor_perflib.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 970f04a958cd..0da85fc2a7e4 100644
--- 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)
 		}
 	}
 
-	pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr->id,
-		       (int)ppc, ppc ? "" : "not");
+	index = ppc;
 
-	pr->performance_platform_limit = (int)ppc;
+	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)))
 		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);
-- 
2.35.3