cpufreq: Allow arch_freq_get_on_cpu to return an error

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@arm.com>
Reviewed-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20250131162439.3843071-2-beata.michalska@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c
index f642de2ebdac8a8112970c4a40361adb4b176d91..6cf31a1649c4b96a5fa20816e980c708b342c799 100644 (file)
--- a/arch/x86/kernel/cpu/aperfmperf.c
+++ b/arch/x86/kernel/cpu/aperfmperf.c
@@ -498,7 +498,7 @@ 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 41ed01f46bd92da5e04f2c14312f24497847bcb0..6571d432cbe339ed4cbff9c9059e980038e3f71b 100644 (file)
--- 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 30ffbddc7ecec72c010a892c4afdace76146d9d7..e69b0e39654cab5dffc14431945e137e87c18956 100644 (file)
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -729,18 +729,18 @@ 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 = sysfs_emit(buf, "%u\n", freq);
        else if (cpufreq_driver->setpolicy && cpufreq_driver->get)
                ret = sysfs_emit(buf, "%u\n", cpufreq_driver->get(policy->cpu));

diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 7fe0981a7e4674f801201c11e7ebaf9c1b9e34d9..02fd4746231dae965ab748257044ed5c88dcff0a 100644 (file)
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -1184,7 +1184,7 @@ 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