[SRU][N:gcp][PATCH 092/109] cpufreq: Allow arch_freq_get_on_cpu to return an error

[Tim Whisonant]

From: Beata Michalska <beata.michalska at arm.com>

BugLink: https://bugs.launchpad.net/bugs/2111859

Allow arch_freq_get_on_cpu to return an error for cases when retrieving
current CPU frequency is not possible, whether that being due to lack of
required arch support or due to other circumstances when the current
frequency cannot be determined at given point of time.

Signed-off-by: Beata Michalska <beata.michalska at arm.com>
Reviewed-by: Prasanna Kumar T S M <ptsm at linux.microsoft.com>
Acked-by: Viresh Kumar <viresh.kumar at linaro.org>
Acked-by: Rafael J. Wysocki <rafael at kernel.org>
Link: https://lore.kernel.org/r/20250131162439.3843071-2-beata.michalska@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
(backported from commit 38e480d4fcac2e191e2f24f381aa8957865c49b2)
[tswhison: adjusted context due to missing commit
5e62d53c763a ("cpufreq: update to sysfs_emit() for safer buffer handling")]
Signed-off-by: Tim Whisonant <tim.whisonant at canonical.com>
---
 arch/x86/kernel/cpu/aperfmperf.c | 2 +-
 arch/x86/kernel/cpu/proc.c       | 7 +++++--
 drivers/cpufreq/cpufreq.c        | 8 ++++----
 include/linux/cpufreq.h          | 2 +-
 4 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c
index fdbb5f07448f..ab646aee6387 100644
--- a/arch/x86/kernel/cpu/aperfmperf.c
+++ b/arch/x86/kernel/cpu/aperfmperf.c
@@ -411,7 +411,7 @@ void arch_scale_freq_tick(void)
  */
 #define MAX_SAMPLE_AGE	((unsigned long)HZ / 50)
 
-unsigned int arch_freq_get_on_cpu(int cpu)
+int arch_freq_get_on_cpu(int cpu)
 {
 	struct aperfmperf *s = per_cpu_ptr(&cpu_samples, cpu);
 	unsigned int seq, freq;
diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index e65fae63660e..471d227e9eae 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -86,9 +86,12 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 		seq_printf(m, "microcode\t: 0x%x\n", c->microcode);
 
 	if (cpu_has(c, X86_FEATURE_TSC)) {
-		unsigned int freq = arch_freq_get_on_cpu(cpu);
+		int freq = arch_freq_get_on_cpu(cpu);
 
-		seq_printf(m, "cpu MHz\t\t: %u.%03u\n", freq / 1000, (freq % 1000));
+		if (freq < 0)
+			seq_puts(m, "cpu MHz\t\t: Unknown\n");
+		else
+			seq_printf(m, "cpu MHz\t\t: %u.%03u\n", freq / 1000, (freq % 1000));
 	}
 
 	/* Cache size */
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 5177ccf42298..1333a73801d1 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -739,18 +739,18 @@ show_one(cpuinfo_transition_latency, cpuinfo.transition_latency);
 show_one(scaling_min_freq, min);
 show_one(scaling_max_freq, max);
 
-__weak unsigned int arch_freq_get_on_cpu(int cpu)
+__weak int arch_freq_get_on_cpu(int cpu)
 {
-	return 0;
+	return -EOPNOTSUPP;
 }
 
 static ssize_t show_scaling_cur_freq(struct cpufreq_policy *policy, char *buf)
 {
 	ssize_t ret;
-	unsigned int freq;
+	int freq;
 
 	freq = arch_freq_get_on_cpu(policy->cpu);
-	if (freq)
+	if (freq > 0)
 		ret = sprintf(buf, "%u\n", freq);
 	else if (cpufreq_driver->setpolicy && cpufreq_driver->get)
 		ret = sprintf(buf, "%u\n", cpufreq_driver->get(policy->cpu));
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index d5bd4b1ceacf..094d99d23e99 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -1202,7 +1202,7 @@ static inline int of_perf_domain_get_sharing_cpumask(int pcpu, const char *list_
 }
 #endif
 
-extern unsigned int arch_freq_get_on_cpu(int cpu);
+extern int arch_freq_get_on_cpu(int cpu);
 
 #ifndef arch_set_freq_scale
 static __always_inline
-- 
2.43.0