Re: [PATCH v9 1/5] cpufreq: Allow arch_freq_get_on_cpu to return an error

Viresh Kumar
2025-01-21T10:47:09Z

On 21-01-25, 08:44, Beata Michalska wrote:
> 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>
> ---
> 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 f642de2ebdac..6cf31a1649c4 100644
> --- 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 41ed01f46bd9..d79f5845a463 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 418236fef172..6f45684483c4 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -728,18 +728,18 @@ 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)

>= ?

Since we can return error now, 0 should be considered a valid
frequency value ?

> 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 7fe0981a7e46..02fd4746231d 100644
> --- 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
> --
> 2.25.1

--
viresh