From 0a1416a49e63c320f6e6c1c8d07e1b58c0d4a3f3 Mon Sep 17 00:00:00 2001 From: Prashant Malani Date: Tue, 22 Jul 2025 05:55:40 +0000 Subject: [PATCH] cpufreq: CPPC: Mark driver with NEED_UPDATE_LIMITS flag AMU counters on certain CPPC-based platforms tend to yield inaccurate delivered performance measurements on systems that are idle/mostly idle. This results in an inaccurate frequency being stored by cpufreq in its policy structure when the CPU is brought online. [1] Consequently, if the userspace governor tries to set the frequency to a new value, there is a possibility that it would be the erroneous value stored earlier. In such a scenario, cpufreq would assume that the requested frequency has already been set and return early, resulting in the correct/new frequency request never making it to the hardware. Since the operating frequency is liable to this sort of inconsistency, mark the CPPC driver with CPUFREQ_NEED_UPDATE_LIMITS so that it is always invoked when a target frequency update is requested. Link: https://lore.kernel.org/linux-pm/20250619000925.415528-3-pmalani@google.com/ [1] Suggested-by: Rafael J. Wysocki Signed-off-by: Prashant Malani Acked-by: Viresh Kumar Link: https://patch.msgid.link/20250722055611.130574-2-pmalani@google.com Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cppc_cpufreq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index a1fd0ff22bc55..4a17162a392da 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -910,7 +910,7 @@ static struct freq_attr *cppc_cpufreq_attr[] = { }; static struct cpufreq_driver cppc_cpufreq_driver = { - .flags = CPUFREQ_CONST_LOOPS, + .flags = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS, .verify = cppc_verify_policy, .target = cppc_cpufreq_set_target, .get = cppc_cpufreq_get_rate, -- 2.47.2