FAILED: patch "[PATCH] cpufreq: CPPC: Avoid using CPUFREQ_ETERNAL as transition" failed to apply to 6.12-stable tree

PATCH New [email protected] 2 participants 2 messages Oct 16, 2025 – Oct 18, 2025

Subsystems (3)

Stable branch CPU frequency scaling framework CPU frequency drivers - CPPC cpufreq

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[email protected]

author maintainer

2025-10-16 14:25 UTC #0 lore raw

The patch below does not apply to the 6.12-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 <[email protected]>.

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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x f965d111e68f4a993cc44d487d416e3d954eea11
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025101610-twistable-shaping-5da2@gregkh' --subject-prefix 'PATCH 6.12.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" <[email protected]>
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+ <[email protected]> # 5.19

Signed-off-by Rafael J. Wysocki <[email protected]>

Reviewed-by Mario Limonciello (AMD) <[email protected]>

Reviewed-by Jie Zhan <[email protected]>

Acked-by Viresh Kumar <[email protected]>

Reviewed-by Qais Yousef <[email protected]>

drivers/cpufreq/cppc_cpufreq.c +12 -2

index 12de0ac7bbaf..b71946937c52 100644
@@ -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

Sasha Levin

maintainer

2025-10-18 16:13 UTC #1 lore raw

PATCH 1/1 cpufreq: CPPC: Avoid using CPUFREQ_ETERNAL as transition delay

From: "Rafael J. Wysocki" <[email protected]>

[ Upstream commit f965d111e68f4a993cc44d487d416e3d954eea11 ]

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+ <[email protected]> # 5.19

Signed-off-by Rafael J. Wysocki <[email protected]>

Reviewed-by Mario Limonciello (AMD) <[email protected]>

Reviewed-by Jie Zhan <[email protected]>

Acked-by Viresh Kumar <[email protected]>

Reviewed-by Qais Yousef <[email protected]>

[ added CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS definition to include/linux/cpufreq.h ]

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/cpufreq/cppc_cpufreq.c | 14 ++++++++++++--
 include/linux/cpufreq.h        |  3 +++
 2 files changed, 15 insertions(+), 2 deletions(-)

drivers/cpufreq/cppc_cpufreq.c +12 -2

index 8d5279c21e6cf..1abedcae50b26 100644
@@ -339,6 +339,16 @@ 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

@@ -361,12 +371,12 @@ 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

include/linux/cpufreq.h +3 -0

index a604c54ae44da..794e38320f568 100644
@@ -32,6 +32,9 @@
  */
 
 #define CPUFREQ_ETERNAL			(-1)
+
+#define CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS	NSEC_PER_MSEC
+
 #define CPUFREQ_NAME_LEN		16
 /* Print length for names. Extra 1 space for accommodating '\n' in prints */
 #define CPUFREQ_NAME_PLEN		(CPUFREQ_NAME_LEN + 1)

Signature · 1 line

2.51.0