linux-kernel - [PATCH 2/2] cpufreq: CPPC: Don't verify cur frequency on governor start

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Message-ID: <20250823001937.2765316-5-pmalani@google.com>
Date: Sat, 23 Aug 2025 00:17:50 +0000
From: Prashant Malani <pmalani@...gle.com>
To: open list <linux-kernel@...r.kernel.org>, 
	"open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Viresh Kumar <viresh.kumar@...aro.org>
Cc: Beata Michalska <beata.michalska@....com>, Prashant Malani <pmalani@...gle.com>
Subject: [PATCH 2/2] cpufreq: CPPC: Don't verify cur frequency on governor start

Opt in to not verifying the policy's current frequency when the governor
starts. CPPC's get() function is known to return unreliable values,
so checking against that can mean the frequency gets set to the
unreliable value even though the governor (and user) didn't intend to do
so. That in turn causes unexpected performance drops.

Cc: Beata Michalska <beata.michalska@....com>
Signed-off-by: Prashant Malani <pmalani@...gle.com>
---
 drivers/cpufreq/cppc_cpufreq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 4a17162a392d..7fd6c03bb726 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -910,7 +910,8 @@ static struct freq_attr *cppc_cpufreq_attr[] = {
 };
 
 static struct cpufreq_driver cppc_cpufreq_driver = {
-	.flags = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
+	.flags = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS |
+		 CPUFREQ_DONT_VERIFY_FREQ_ON_GOVERNOR_START,
 	.verify = cppc_verify_policy,
 	.target = cppc_cpufreq_set_target,
 	.get = cppc_cpufreq_get_rate,
-- 
2.51.0.rc2.233.g662b1ed5c5-goog