The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x f965d111e68f4a993cc44d487d416e3d954eea11 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025101655-grandma-populate-0fb4@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f965d111e68f4a993cc44d487d416e3d954eea11 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com Date: Fri, 26 Sep 2025 12:19:41 +0200 Subject: [PATCH] cpufreq: CPPC: Avoid using CPUFREQ_ETERNAL as transition delay
If cppc_get_transition_latency() returns CPUFREQ_ETERNAL to indicate a failure to retrieve the transition latency value from the platform firmware, the CPPC cpufreq driver will use that value (converted to microseconds) as the policy transition delay, but it is way too large for any practical use.
Address this by making the driver use the cpufreq's default transition latency value (in microseconds) as the transition delay if CPUFREQ_ETERNAL is returned by cppc_get_transition_latency().
Fixes: d4f3388afd48 ("cpufreq / CPPC: Set platform specific transition_delay_us") Cc: 5.19+ stable@vger.kernel.org # 5.19 Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Mario Limonciello (AMD) superm1@kernel.org Reviewed-by: Jie Zhan zhanjie9@hisilicon.com Acked-by: Viresh Kumar viresh.kumar@linaro.org Reviewed-by: Qais Yousef qyousef@layalina.io
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index 12de0ac7bbaf..b71946937c52 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -308,6 +308,16 @@ static int cppc_verify_policy(struct cpufreq_policy_data *policy) return 0; }
+static unsigned int __cppc_cpufreq_get_transition_delay_us(unsigned int cpu) +{ + unsigned int transition_latency_ns = cppc_get_transition_latency(cpu); + + if (transition_latency_ns == CPUFREQ_ETERNAL) + return CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS / NSEC_PER_USEC; + + return transition_latency_ns / NSEC_PER_USEC; +} + /* * The PCC subspace describes the rate at which platform can accept commands * on the shared PCC channel (including READs which do not count towards freq @@ -330,12 +340,12 @@ static unsigned int cppc_cpufreq_get_transition_delay_us(unsigned int cpu) return 10000; } } - return cppc_get_transition_latency(cpu) / NSEC_PER_USEC; + return __cppc_cpufreq_get_transition_delay_us(cpu); } #else static unsigned int cppc_cpufreq_get_transition_delay_us(unsigned int cpu) { - return cppc_get_transition_latency(cpu) / NSEC_PER_USEC; + return __cppc_cpufreq_get_transition_delay_us(cpu); } #endif