* [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency
@ 2022-03-11 8:11 z00314508
2022-03-11 8:33 ` Greg KH
2022-03-11 15:52 ` Rafael J. Wysocki
0 siblings, 2 replies; 5+ messages in thread
From: z00314508 @ 2022-03-11 8:11 UTC (permalink / raw)
To: rafael, viresh.kumar, tglx, len.brown
Cc: zhengzucheng, linux-pm, linux-kernel, stable
From: Zucheng Zheng <zhengzucheng@huawei.com>
On some specific platforms, the cpufreq driver does not define
cpufreq_driver.get() routine (eg:x86 intel_pstate driver), as a
result, the cpufreq_get() can't get the correct CPU frequency.
Modern x86 processors include the hardware needed to accurately
calculate frequency over an interval -- APERF, MPERF and the TSC.
Here we use arch_freq_get_on_cpu() in preference to any driver
driver-specific cpufreq_driver.get() routine to get CPU frequency.
Fixes: f8475cef9008 ("x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF")
Signed-off-by: Zucheng Zheng <zhengzucheng@huawei.com>
---
drivers/cpufreq/cpufreq.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 80f535cc8a75..d777257b4454 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1806,10 +1806,14 @@ unsigned int cpufreq_get(unsigned int cpu)
{
struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
unsigned int ret_freq = 0;
+ unsigned int freq;
if (policy) {
down_read(&policy->rwsem);
- if (cpufreq_driver->get)
+ freq = arch_freq_get_on_cpu(policy->cpu);
+ if (freq)
+ ret_freq = freq;
+ else if (cpufreq_driver->get)
ret_freq = __cpufreq_get(policy);
up_read(&policy->rwsem);
--
2.18.0.huawei.25
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency
2022-03-11 8:11 [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency z00314508
@ 2022-03-11 8:33 ` Greg KH
2022-03-11 15:52 ` Rafael J. Wysocki
1 sibling, 0 replies; 5+ messages in thread
From: Greg KH @ 2022-03-11 8:33 UTC (permalink / raw)
To: z00314508
Cc: rafael, viresh.kumar, tglx, len.brown, linux-pm, linux-kernel, stable
On Fri, Mar 11, 2022 at 04:11:11PM +0800, z00314508 wrote:
> From: Zucheng Zheng <zhengzucheng@huawei.com>
>
> On some specific platforms, the cpufreq driver does not define
> cpufreq_driver.get() routine (eg:x86 intel_pstate driver), as a
> result, the cpufreq_get() can't get the correct CPU frequency.
>
> Modern x86 processors include the hardware needed to accurately
> calculate frequency over an interval -- APERF, MPERF and the TSC.
> Here we use arch_freq_get_on_cpu() in preference to any driver
> driver-specific cpufreq_driver.get() routine to get CPU frequency.
>
> Fixes: f8475cef9008 ("x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF")
> Signed-off-by: Zucheng Zheng <zhengzucheng@huawei.com>
> ---
> drivers/cpufreq/cpufreq.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 80f535cc8a75..d777257b4454 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1806,10 +1806,14 @@ unsigned int cpufreq_get(unsigned int cpu)
> {
> struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> unsigned int ret_freq = 0;
> + unsigned int freq;
>
> if (policy) {
> down_read(&policy->rwsem);
> - if (cpufreq_driver->get)
> + freq = arch_freq_get_on_cpu(policy->cpu);
> + if (freq)
> + ret_freq = freq;
> + else if (cpufreq_driver->get)
> ret_freq = __cpufreq_get(policy);
> up_read(&policy->rwsem);
>
> --
> 2.18.0.huawei.25
>
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency
2022-03-11 8:11 [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency z00314508
2022-03-11 8:33 ` Greg KH
@ 2022-03-11 15:52 ` Rafael J. Wysocki
2022-03-15 2:30 ` zhengzucheng
1 sibling, 1 reply; 5+ messages in thread
From: Rafael J. Wysocki @ 2022-03-11 15:52 UTC (permalink / raw)
To: z00314508
Cc: Rafael J. Wysocki, Viresh Kumar, Thomas Gleixner, Len Brown,
Linux PM, Linux Kernel Mailing List, Stable
On Fri, Mar 11, 2022 at 9:11 AM z00314508 <zhengzucheng@huawei.com> wrote:
>
> From: Zucheng Zheng <zhengzucheng@huawei.com>
>
> On some specific platforms, the cpufreq driver does not define
> cpufreq_driver.get() routine (eg:x86 intel_pstate driver), as a
I guess you mean the cpufreq driver ->get callback.
No, intel_pstate doesn't implement it, because it cannot reliably
return the current CPU frequency.
> result, the cpufreq_get() can't get the correct CPU frequency.
No, it can't, if intel_pstate is the driver, but what's the problem?
This function is only called in one place in the kernel and not on x8
even.
> Modern x86 processors include the hardware needed to accurately
> calculate frequency over an interval -- APERF, MPERF and the TSC.
You can compute the average frequency over an interval, but ->get is
expected to return the actual current frequency at the time call time.
> Here we use arch_freq_get_on_cpu() in preference to any driver
> driver-specific cpufreq_driver.get() routine to get CPU frequency.
>
> Fixes: f8475cef9008 ("x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF")
No kidding.
> Signed-off-by: Zucheng Zheng <zhengzucheng@huawei.com>
> ---
> drivers/cpufreq/cpufreq.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 80f535cc8a75..d777257b4454 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1806,10 +1806,14 @@ unsigned int cpufreq_get(unsigned int cpu)
> {
> struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> unsigned int ret_freq = 0;
> + unsigned int freq;
>
> if (policy) {
> down_read(&policy->rwsem);
> - if (cpufreq_driver->get)
> + freq = arch_freq_get_on_cpu(policy->cpu);
> + if (freq)
> + ret_freq = freq;
> + else if (cpufreq_driver->get)
Again, what problem exactly does this address?
> ret_freq = __cpufreq_get(policy);
> up_read(&policy->rwsem);
>
> --
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency
2022-03-11 15:52 ` Rafael J. Wysocki
@ 2022-03-15 2:30 ` zhengzucheng
2022-03-15 10:47 ` Rafael J. Wysocki
0 siblings, 1 reply; 5+ messages in thread
From: zhengzucheng @ 2022-03-15 2:30 UTC (permalink / raw)
To: Rafael J. Wysocki
Cc: Viresh Kumar, Thomas Gleixner, Len Brown, Linux PM,
Linux Kernel Mailing List, Stable
On 2022/3/11 23:52, Rafael J. Wysocki wrote:
> On Fri, Mar 11, 2022 at 9:11 AM z00314508 <zhengzucheng@huawei.com> wrote:
>> From: Zucheng Zheng <zhengzucheng@huawei.com>
>>
>> On some specific platforms, the cpufreq driver does not define
>> cpufreq_driver.get() routine (eg:x86 intel_pstate driver), as a
> I guess you mean the cpufreq driver ->get callback.
>
> No, intel_pstate doesn't implement it, because it cannot reliably
> return the current CPU frequency.
>
>> result, the cpufreq_get() can't get the correct CPU frequency.
> No, it can't, if intel_pstate is the driver, but what's the problem?
> This function is only called in one place in the kernel and not on x8
> even.
>
>> Modern x86 processors include the hardware needed to accurately
>> calculate frequency over an interval -- APERF, MPERF and the TSC.
> You can compute the average frequency over an interval, but ->get is
> expected to return the actual current frequency at the time call time.
>
>> Here we use arch_freq_get_on_cpu() in preference to any driver
>> driver-specific cpufreq_driver.get() routine to get CPU frequency.
>>
>> Fixes: f8475cef9008 ("x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF")
> No kidding.
>
>> Signed-off-by: Zucheng Zheng <zhengzucheng@huawei.com>
>> ---
>> drivers/cpufreq/cpufreq.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 80f535cc8a75..d777257b4454 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1806,10 +1806,14 @@ unsigned int cpufreq_get(unsigned int cpu)
>> {
>> struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
>> unsigned int ret_freq = 0;
>> + unsigned int freq;
>>
>> if (policy) {
>> down_read(&policy->rwsem);
>> - if (cpufreq_driver->get)
>> + freq = arch_freq_get_on_cpu(policy->cpu);
>> + if (freq)
>> + ret_freq = freq;
>> + else if (cpufreq_driver->get)
> Again, what problem exactly does this address?
Thank you for review.
In some scenarios, cpufreq driver ->get is not defined,
some driver get the CPU frequency by calling cpufreq_get() will return 0.
The modification to this problem is inspired by the implementation of
the show_scaling_cur_freq().
>
>> ret_freq = __cpufreq_get(policy);
>> up_read(&policy->rwsem);
>>
>> --
> .
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency
2022-03-15 2:30 ` zhengzucheng
@ 2022-03-15 10:47 ` Rafael J. Wysocki
0 siblings, 0 replies; 5+ messages in thread
From: Rafael J. Wysocki @ 2022-03-15 10:47 UTC (permalink / raw)
To: zhengzucheng
Cc: Rafael J. Wysocki, Viresh Kumar, Thomas Gleixner, Len Brown,
Linux PM, Linux Kernel Mailing List, Stable
On Tue, Mar 15, 2022 at 3:30 AM zhengzucheng <zhengzucheng@huawei.com> wrote:
>
>
>
> On 2022/3/11 23:52, Rafael J. Wysocki wrote:
> > On Fri, Mar 11, 2022 at 9:11 AM z00314508 <zhengzucheng@huawei.com> wrote:
> >> From: Zucheng Zheng <zhengzucheng@huawei.com>
> >>
> >> On some specific platforms, the cpufreq driver does not define
> >> cpufreq_driver.get() routine (eg:x86 intel_pstate driver), as a
> > I guess you mean the cpufreq driver ->get callback.
> >
> > No, intel_pstate doesn't implement it, because it cannot reliably
> > return the current CPU frequency.
> >
> >> result, the cpufreq_get() can't get the correct CPU frequency.
> > No, it can't, if intel_pstate is the driver, but what's the problem?
> > This function is only called in one place in the kernel and not on x8
> > even.
> >
> >> Modern x86 processors include the hardware needed to accurately
> >> calculate frequency over an interval -- APERF, MPERF and the TSC.
> > You can compute the average frequency over an interval, but ->get is
> > expected to return the actual current frequency at the time call time.
> >
> >> Here we use arch_freq_get_on_cpu() in preference to any driver
> >> driver-specific cpufreq_driver.get() routine to get CPU frequency.
> >>
> >> Fixes: f8475cef9008 ("x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF")
> > No kidding.
> >
> >> Signed-off-by: Zucheng Zheng <zhengzucheng@huawei.com>
> >> ---
> >> drivers/cpufreq/cpufreq.c | 6 +++++-
> >> 1 file changed, 5 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> >> index 80f535cc8a75..d777257b4454 100644
> >> --- a/drivers/cpufreq/cpufreq.c
> >> +++ b/drivers/cpufreq/cpufreq.c
> >> @@ -1806,10 +1806,14 @@ unsigned int cpufreq_get(unsigned int cpu)
> >> {
> >> struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> >> unsigned int ret_freq = 0;
> >> + unsigned int freq;
> >>
> >> if (policy) {
> >> down_read(&policy->rwsem);
> >> - if (cpufreq_driver->get)
> >> + freq = arch_freq_get_on_cpu(policy->cpu);
> >> + if (freq)
> >> + ret_freq = freq;
> >> + else if (cpufreq_driver->get)
> > Again, what problem exactly does this address?
> Thank you for review.
>
> In some scenarios, cpufreq driver ->get is not defined,
> some driver get the CPU frequency by calling cpufreq_get() will return 0.
Which driver? Again, there is only one calling cpufreq_get() in the
kernel tree and it is not on x86.
> The modification to this problem is inspired by the implementation of
> the show_scaling_cur_freq().
> >
> >> ret_freq = __cpufreq_get(policy);
> >> up_read(&policy->rwsem);
> >>
> >> --
The answer to my question appears to be that you want cpufreq_get() to
be consistent with show_scaling_cur_freq().
Fair enough, but in that case please make them both call the same
lower-level routine implementing the desired behavior so as to avoid
code duplication.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-03-15 10:49 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-03-11 8:11 [PATCH] cpufreq: fix cpufreq_get() can't get correct CPU frequency z00314508
2022-03-11 8:33 ` Greg KH
2022-03-11 15:52 ` Rafael J. Wysocki
2022-03-15 2:30 ` zhengzucheng
2022-03-15 10:47 ` Rafael J. Wysocki
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).