linux-kernel - [PATCH v1 3/4] ACPI: CPPC: Replace CPUFREQ

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Message-ID: <3925838.kQq0lBPeGt@rafael.j.wysocki>
Date: Thu, 25 Sep 2025 17:46:27 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: Shawn Guo <shawnguo@...nel.org>, Qais Yousef <qyousef@...alina.io>,
 LKML <linux-kernel@...r.kernel.org>, Viresh Kumar <viresh.kumar@...aro.org>,
 Prashanth Prakash <pprakash@...eaurora.org>,
 Pierre Gondois <pierre.gondois@....com>,
 Mario Limonciello <mario.limonciello@....com>,
 Linux ACPI <linux-acpi@...r.kernel.org>
Subject:
 [PATCH v1 3/4] ACPI: CPPC: Replace CPUFREQ_ETERNAL with CPPC-specific symbol

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Instead of using CPUFREQ_ETERNAL for signaling error conditions in
cppc_get_transition_latency(), introduce CPPC_NO_DATA specifically
for this purpose and update all of the callers of this function to
use it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/acpi/cppc_acpi.c       |    6 +++---
 drivers/cpufreq/amd-pstate.c   |    4 ++--
 drivers/cpufreq/cppc_cpufreq.c |    2 +-
 include/acpi/cppc_acpi.h       |    4 +++-
 include/linux/cpufreq.h        |    3 ---
 5 files changed, 9 insertions(+), 10 deletions(-)

--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1897,16 +1897,16 @@ unsigned int cppc_get_transition_latency
 
 	cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
 	if (!cpc_desc)
-		return CPUFREQ_ETERNAL;
+		return CPPC_NO_DATA;
 
 	desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
 	if (CPC_IN_SYSTEM_MEMORY(desired_reg) || CPC_IN_SYSTEM_IO(desired_reg))
 		return 0;
 	else if (!CPC_IN_PCC(desired_reg))
-		return CPUFREQ_ETERNAL;
+		return CPPC_NO_DATA;
 
 	if (pcc_ss_id < 0)
-		return CPUFREQ_ETERNAL;
+		return CPPC_NO_DATA;
 
 	pcc_ss_data = pcc_data[pcc_ss_id];
 	if (pcc_ss_data->pcc_mpar)
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -875,7 +875,7 @@ static u32 amd_pstate_get_transition_del
 	u32 transition_delay_ns;
 
 	transition_delay_ns = cppc_get_transition_latency(cpu);
-	if (transition_delay_ns == CPUFREQ_ETERNAL) {
+	if (transition_delay_ns == CPPC_NO_DATA) {
 		if (cpu_feature_enabled(X86_FEATURE_AMD_FAST_CPPC))
 			return AMD_PSTATE_FAST_CPPC_TRANSITION_DELAY;
 		else
@@ -894,7 +894,7 @@ static u32 amd_pstate_get_transition_lat
 	u32 transition_latency;
 
 	transition_latency = cppc_get_transition_latency(cpu);
-	if (transition_latency  == CPUFREQ_ETERNAL)
+	if (transition_latency  == CPPC_NO_DATA)
 		return AMD_PSTATE_TRANSITION_LATENCY;
 
 	return transition_latency;
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -312,7 +312,7 @@ static unsigned int get_transition_laten
 {
 	unsigned int transition_latency_ns = cppc_get_transition_latency(cpu);
 
-	if (transition_latency_ns == CPUFREQ_ETERNAL)
+	if (transition_latency_ns == CPPC_NO_DATA)
 		return CPUFREQ_DEFAULT_TRANSITION_LATENCY_NS / NSEC_PER_USEC;
 
 	return transition_latency_ns / NSEC_PER_USEC;
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -41,6 +41,8 @@
 
 #define CPPC_ENERGY_PERF_MAX	(0xFF)
 
+#define CPPC_NO_DATA	(unsigned int)(-1)
+
 /* Each register has the folowing format. */
 struct cpc_reg {
 	u8 descriptor;
@@ -218,7 +220,7 @@ static inline bool cppc_allow_fast_switc
 }
 static inline unsigned int cppc_get_transition_latency(int cpu)
 {
-	return CPUFREQ_ETERNAL;
+	return CPPC_NO_DATA;
 }
 static inline bool cpc_ffh_supported(void)
 {