| Message ID | 20250121084435.2839280-2-beata.michalska@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v9,1/5] cpufreq: Allow arch_freq_get_on_cpu to return an error | expand |
On 21-01-2025 14:14, 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) > 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 Looks good to me. Reviewed-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
On Tue, Jan 21, 2025 at 04:17:06PM +0530, Viresh Kumar wrote: > 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 ? Theoretically speaking - it should, though what would 0 actually represent then ? --- BR Beata > > > 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
On 21-01-25, 16:14, Beata Michalska wrote: > Theoretically speaking - it should, though what would 0 actually > represent then ? 0 won't be a failure, that's clear, since errors are represented differently now. I am not sure what 0 frequency would mean and it can be left as an architecture specific value, which is a corner case I am not sure will ever occur.
On Wed, Jan 22, 2025 at 11:42:50AM +0530, Viresh Kumar wrote: > On 21-01-25, 16:14, Beata Michalska wrote: > > Theoretically speaking - it should, though what would 0 actually > > represent then ? > > 0 won't be a failure, that's clear, since errors are represented > differently now. I am not sure what 0 frequency would mean and it can > be left as an architecture specific value, which is a corner case I am > not sure will ever occur. That would mean we are opting for presenting '0' value (whatever that means) instead of trying alternative ways of getting 'current' frequency ? This is still the scaling_cur_freq. --- BR Beata > > -- > viresh
On 23-01-25, 22:45, Beata Michalska wrote: > That would mean we are opting for presenting '0' value (whatever that means) > instead of trying alternative ways of getting 'current' frequency ? > This is still the scaling_cur_freq. A return value of 0 should typically mean something went wrong somewhere and didn't return the right value to us. - For the print message, I think we should just print the value instead of UNKNOWN. Let the user / developer decide what to do with it. - As for trying other mechanism to find the frequency now, maybe you are right and looking for an alternate way is the right way to go. And that would be consistent with existing behavior too.
On Fri, Jan 24, 2025 at 09:03:33AM +0530, Viresh Kumar wrote: > On 23-01-25, 22:45, Beata Michalska wrote: > > That would mean we are opting for presenting '0' value (whatever that means) > > instead of trying alternative ways of getting 'current' frequency ? > > This is still the scaling_cur_freq. > > A return value of 0 should typically mean something went wrong > somewhere and didn't return the right value to us. If smth goes wrong, an error should be returned, shoulnd't it? > > - For the print message, I think we should just print the value > instead of UNKNOWN. Let the user / developer decide what to do with > it. Are you refering to the x86 show_cpuinfo behaviour altered by this patch ? > > - As for trying other mechanism to find the frequency now, maybe you > are right and looking for an alternate way is the right way to go. > And that would be consistent with existing behavior too. > That would mean that changes to show_scaling_cur_freq are fine ? Just trying to clarify things. Thank you. --- BR Beata > -- > viresh
On 28-01-25, 09:09, Beata Michalska wrote: > On Fri, Jan 24, 2025 at 09:03:33AM +0530, Viresh Kumar wrote: > > On 23-01-25, 22:45, Beata Michalska wrote: > > > That would mean we are opting for presenting '0' value (whatever that means) > > > instead of trying alternative ways of getting 'current' frequency ? > > > This is still the scaling_cur_freq. > > > > A return value of 0 should typically mean something went wrong > > somewhere and didn't return the right value to us. > If smth goes wrong, an error should be returned, shoulnd't it? Right, but what if no error is detected and still a value of 0 is returned somehow ? That's what I was talking about. > > - For the print message, I think we should just print the value > > instead of UNKNOWN. Let the user / developer decide what to do with > > it. > Are you refering to the x86 show_cpuinfo behaviour altered by this patch ? Yes > > - As for trying other mechanism to find the frequency now, maybe you > > are right and looking for an alternate way is the right way to go. > > And that would be consistent with existing behavior too. > > > That would mean that changes to show_scaling_cur_freq are fine ? Yes.
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) 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
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(-)