[PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Pratyush Yadav]

When a processor is brought offline and online again, it is unable to
use Turbo mode because the _PSS table does not contain the whole turbo
frequency range, but only +1 MHz above the max non-turbo frequency. This
causes problems when ACPI processor driver tries to set frequency
constraints. See patch 2 for more details.

Pratyush Yadav (2):
  acpi: processor: allow fixing up the frequency for a performance state
  cpufreq: intel_pstate: use acpi perflib to update turbo frequency

 drivers/acpi/processor_perflib.c | 40 ++++++++++++++++++++++++++++++++
 drivers/cpufreq/intel_pstate.c   |  5 ++--
 include/acpi/processor.h         |  2 ++
 3 files changed, 45 insertions(+), 2 deletions(-)

--
2.38.1

[PATCH 1/2] acpi: processor: allow fixing up the frequency for a performance state

[Pratyush Yadav]

In some cases the ACPI table can have an incorrect frequency populated
for a performance state. For example, in Intel platforms, the Turbo
frequency is just listed as +1 MHz above the max non-turbo frequency.
The frequency can actually go much higher based on various factors like
temperature, voltage, etc.

Allow drivers like intel_pstate to fix up performance state frequencies
with the actual maximum value. While at it, also update the QoS
constraints if needed to match the new frequency values.

Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
---
 drivers/acpi/processor_perflib.c | 40 ++++++++++++++++++++++++++++++++
 include/acpi/processor.h         |  2 ++
 2 files changed, 42 insertions(+)

diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 970f04a958cd..4958aee4c024 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -766,3 +766,43 @@ void acpi_processor_unregister_performance(unsigned int cpu)
 	mutex_unlock(&performance_mutex);
 }
 EXPORT_SYMBOL(acpi_processor_unregister_performance);
+
+int acpi_processor_fixup_perf_state(unsigned int cpu, unsigned int state,
+				    unsigned int frequency)
+{
+	struct acpi_processor *pr;
+	int ret;
+
+	mutex_lock(&performance_mutex);
+
+	pr = per_cpu(processors, cpu);
+	if (!pr) {
+		mutex_unlock(&performance_mutex);
+		return -ENODEV;
+	}
+
+	if (!pr->performance) {
+		mutex_unlock(&performance_mutex);
+		return -EINVAL;
+	}
+
+	if (state >= pr->performance->state_count) {
+		mutex_unlock(&performance_mutex);
+		return -EINVAL;
+	}
+
+	pr->performance->states[state].core_frequency = frequency;
+
+	if (ignore_ppc != 1 && state == pr->performance_platform_limit &&
+	    freq_qos_request_active(&pr->perflib_req)) {
+		ret = freq_qos_update_request(&pr->perflib_req,
+					      frequency * 1000);
+		if (ret < 0)
+			pr_warn("Failed to update perflib freq constraint: CPU%d (%d)\n",
+				pr->id, ret);
+	}
+
+	mutex_unlock(&performance_mutex);
+	return 0;
+}
+EXPORT_SYMBOL(acpi_processor_fixup_perf_state);
diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index 94181fe9780a..daff978cfa7d 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -258,6 +258,8 @@ extern int acpi_processor_preregister_performance(struct
 extern int acpi_processor_register_performance(struct acpi_processor_performance
 					       *performance, unsigned int cpu);
 extern void acpi_processor_unregister_performance(unsigned int cpu);
+extern int acpi_processor_fixup_perf_state(unsigned int cpu, unsigned int state,
+					   unsigned int frequency);
 
 int acpi_processor_pstate_control(void);
 /* note: this locks both the calling module and the processor module
-- 
2.38.1

Re: [PATCH 1/2] acpi: processor: allow fixing up the frequency for a performance state

[Rafael J. Wysocki]

On Wed, Dec 21, 2022 at 4:52 PM Pratyush Yadav <ptyadav@amazon.de> wrote:
>
> In some cases the ACPI table can have an incorrect frequency populated
> for a performance state. For example, in Intel platforms, the Turbo
> frequency is just listed as +1 MHz above the max non-turbo frequency.

Which is a known convention based on compatibility with some older OSes.

> The frequency can actually go much higher based on various factors like
> temperature, voltage, etc.

It can.

> Allow drivers like intel_pstate to fix up performance state frequencies
> with the actual maximum value.

Why do you want to do that?

> While at it, also update the QoS
> constraints if needed to match the new frequency values.
>
> Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
> ---
>  drivers/acpi/processor_perflib.c | 40 ++++++++++++++++++++++++++++++++
>  include/acpi/processor.h         |  2 ++
>  2 files changed, 42 insertions(+)
>
> diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
> index 970f04a958cd..4958aee4c024 100644
> --- a/drivers/acpi/processor_perflib.c
> +++ b/drivers/acpi/processor_perflib.c
> @@ -766,3 +766,43 @@ void acpi_processor_unregister_performance(unsigned int cpu)
>         mutex_unlock(&performance_mutex);
>  }
>  EXPORT_SYMBOL(acpi_processor_unregister_performance);
> +
> +int acpi_processor_fixup_perf_state(unsigned int cpu, unsigned int state,
> +                                   unsigned int frequency)
> +{
> +       struct acpi_processor *pr;
> +       int ret;
> +
> +       mutex_lock(&performance_mutex);
> +
> +       pr = per_cpu(processors, cpu);
> +       if (!pr) {
> +               mutex_unlock(&performance_mutex);
> +               return -ENODEV;
> +       }
> +
> +       if (!pr->performance) {
> +               mutex_unlock(&performance_mutex);
> +               return -EINVAL;
> +       }
> +
> +       if (state >= pr->performance->state_count) {
> +               mutex_unlock(&performance_mutex);
> +               return -EINVAL;
> +       }
> +
> +       pr->performance->states[state].core_frequency = frequency;
> +
> +       if (ignore_ppc != 1 && state == pr->performance_platform_limit &&
> +           freq_qos_request_active(&pr->perflib_req)) {
> +               ret = freq_qos_update_request(&pr->perflib_req,
> +                                             frequency * 1000);
> +               if (ret < 0)
> +                       pr_warn("Failed to update perflib freq constraint: CPU%d (%d)\n",
> +                               pr->id, ret);
> +       }
> +
> +       mutex_unlock(&performance_mutex);
> +       return 0;
> +}
> +EXPORT_SYMBOL(acpi_processor_fixup_perf_state);
> diff --git a/include/acpi/processor.h b/include/acpi/processor.h
> index 94181fe9780a..daff978cfa7d 100644
> --- a/include/acpi/processor.h
> +++ b/include/acpi/processor.h
> @@ -258,6 +258,8 @@ extern int acpi_processor_preregister_performance(struct
>  extern int acpi_processor_register_performance(struct acpi_processor_performance
>                                                *performance, unsigned int cpu);
>  extern void acpi_processor_unregister_performance(unsigned int cpu);
> +extern int acpi_processor_fixup_perf_state(unsigned int cpu, unsigned int state,
> +                                          unsigned int frequency);
>
>  int acpi_processor_pstate_control(void);
>  /* note: this locks both the calling module and the processor module
> --
> 2.38.1
>

Re: [PATCH 1/2] acpi: processor: allow fixing up the frequency for a performance state

[Pratyush Yadav]

On Thu, Dec 22 2022, Rafael J. Wysocki wrote:
> On Wed, Dec 21, 2022 at 4:52 PM Pratyush Yadav <ptyadav@amazon.de> wrote:
>>
>> In some cases the ACPI table can have an incorrect frequency populated
>> for a performance state. For example, in Intel platforms, the Turbo
>> frequency is just listed as +1 MHz above the max non-turbo frequency.
>
> Which is a known convention based on compatibility with some older OSes.

Interesting. I did not know that.

>
>> The frequency can actually go much higher based on various factors like
>> temperature, voltage, etc.
>
> It can.
>
>> Allow drivers like intel_pstate to fix up performance state frequencies
>> with the actual maximum value.
>
> Why do you want to do that?

To be able to use my processors at the full frequency they are capable
of. See [0] for more details.

[0] https://lore.kernel.org/linux-pm/mafs0k02jd8oh.fsf_-_@dev-dsk-ptyadav-1c-37607b33.eu-west-1.amazon.com/

>
[...]

-- 
Regards,
Pratyush Yadav



Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879

[PATCH 2/2] cpufreq: intel_pstate: use acpi perflib to update turbo frequency

[Pratyush Yadav]

The _PSS table does not contain the whole turbo frequency range, but
only +1 MHz above the max non-turbo frequency. The pstate driver then
updates the ACPI perf data with the actual max frequency. But doing this
here directly would mean that frequency QoS constraints that acpi
perflib imposes do not get updated.

This is a problem when a CPU is brought offline and online again. When
the CPU first comes online, cpufreq is not initialized. So PPC
constraints are not applied (because ignore_ppc == -1). This leads to
the frequency QoS allowing all values from acpi perflib side.

Once everything is initialized and then userspace brings a CPU down and
up again, intel_pstate_init_acpi_perf_limits() calls
acpi_processor_register_performance(), which then eventually calls
acpi_processor_get_platform_limit(). There PPC is state 0, the turbo
state, but the frequency has not been updated yet. So when
acpi_processor_get_platform_limit() sets QoS constraints, it sets them
with the max_non_turbo + 1 value.

Now even though intel_pstate says it can support the full turbo speed,
cpufreq only asks for up to max_non_turbo + 1 MHz since that is what
satisfies all constraints.

Call into acpi perflib's function to update the frequency so it can also
update the QoS constraints with the new value.

Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
---
 drivers/cpufreq/intel_pstate.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index fd73d6d2b808..b312f87ff522 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -464,8 +464,9 @@ static void intel_pstate_init_acpi_perf_limits(struct cpufreq_policy *policy)
 	 * Also need to convert to MHz as _PSS freq is in MHz.
 	 */
 	if (!global.turbo_disabled)
-		cpu->acpi_perf_data.states[0].core_frequency =
-					policy->cpuinfo.max_freq / 1000;
+		acpi_processor_fixup_perf_state(policy->cpu, 0,
+						policy->cpuinfo.max_freq / 1000);
+
 	cpu->valid_pss_table = true;
 	pr_debug("_PPC limits will be enforced\n");
 
-- 
2.38.1

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[srinivas pandruvada]

On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> When a processor is brought offline and online again, it is unable to
> use Turbo mode because the _PSS table does not contain the whole
> turbo
> frequency range, but only +1 MHz above the max non-turbo frequency.
> This
> causes problems when ACPI processor driver tries to set frequency
> constraints. See patch 2 for more details.
> 
Are you using some _PPC constraint to force to limit frequency?
I did a offline/online with PPC=0 with no HWP, I can get to full turbo
range.

[  121.237752] smpboot: CPU 1 is now offline
[  125.734886] x86: Booting SMP configuration:
[  125.734892] smpboot: Booting Node 0 Processor 1 APIC 0x2
[  125.741007] intel_pstate: CPU 1 going online
[  125.741692] intel_pstate: CPU1 - ACPI _PSS perf data
[  125.741698] intel_pstate:      *P0: 2301 MHz, 28000 mW, 0x2a00
[  125.741703] intel_pstate:       P1: 2300 MHz, 28000 mW, 0x1700
[  125.741705] intel_pstate:       P2: 2200 MHz, 26297 mW, 0x1600
[  125.741707] intel_pstate:       P3: 2000 MHz, 23263 mW, 0x1400
[  125.741710] intel_pstate:       P4: 1900 MHz, 21924 mW, 0x1300
[  125.741712] intel_pstate:       P5: 1800 MHz, 20612 mW, 0x1200
[  125.741714] intel_pstate:       P6: 1600 MHz, 17812 mW, 0x1000
[  125.741716] intel_pstate:       P7: 1500 MHz, 16581 mW, 0xf00
[  125.741718] intel_pstate:       P8: 1300 MHz, 13946 mW, 0xd00
[  125.741720] intel_pstate:       P9: 1200 MHz, 12796 mW, 0xc00
[  125.741722] intel_pstate:       P10: 1100 MHz, 11426 mW, 0xb00
[  125.741724] intel_pstate:       P11: 900 MHz, 9250 mW, 0x900
[  125.741726] intel_pstate:       P12: 800 MHz, 7965 mW, 0x800
[  125.741729] intel_pstate:       P13: 700 MHz, 6940 mW, 0x700
[  125.741731] intel_pstate:       P14: 500 MHz, 4738 mW, 0x500
[  125.741733] intel_pstate:       P15: 400 MHz, 3787 mW, 0x400
[  125.741735] intel_pstate: _PPC limits will be enforced
[  125.741740] intel_pstate: policy->max > max non turbo frequency
[  125.741742] intel_pstate: cpu:1 min_policy_perf:4 max_policy_perf:42
[  125.741745] intel_pstate: cpu:1 global_min:4 global_max:42
[  125.741747] intel_pstate: cpu:1 max_perf_ratio:42 min_perf_ratio:4
[  125.742243] intel_pstate: policy->max > max non turbo frequency
[  125.742247] intel_pstate: cpu:1 min_policy_perf:4 max_policy_perf:42
[  125.742251] intel_pstate: cpu:1 global_min:4 global_max:42
[  125.742255] intel_pstate: cpu:1 max_perf_ratio:42 min_perf_ratio:4


It is not clear how to get to this non turbo situation.

Thanks,
Srinivas

> Pratyush Yadav (2):
>   acpi: processor: allow fixing up the frequency for a performance
> state
>   cpufreq: intel_pstate: use acpi perflib to update turbo frequency
> 
>  drivers/acpi/processor_perflib.c | 40
> ++++++++++++++++++++++++++++++++
>  drivers/cpufreq/intel_pstate.c   |  5 ++--
>  include/acpi/processor.h         |  2 ++
>  3 files changed, 45 insertions(+), 2 deletions(-)
> 
> --
> 2.38.1
> 

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Pratyush Yadav]

Hi Srinivas,

On Wed, Dec 21 2022, srinivas pandruvada wrote:
> On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
>> When a processor is brought offline and online again, it is unable to
>> use Turbo mode because the _PSS table does not contain the whole
>> turbo
>> frequency range, but only +1 MHz above the max non-turbo frequency.
>> This
>> causes problems when ACPI processor driver tries to set frequency
>> constraints. See patch 2 for more details.
>>
> Are you using some _PPC constraint to force to limit frequency?
> I did a offline/online with PPC=0 with no HWP, I can get to full turbo
> range.
>
> [  121.237752] smpboot: CPU 1 is now offline
> [  125.734886] x86: Booting SMP configuration:
> [  125.734892] smpboot: Booting Node 0 Processor 1 APIC 0x2
> [  125.741007] intel_pstate: CPU 1 going online
> [  125.741692] intel_pstate: CPU1 - ACPI _PSS perf data
> [  125.741698] intel_pstate:      *P0: 2301 MHz, 28000 mW, 0x2a00
> [  125.741703] intel_pstate:       P1: 2300 MHz, 28000 mW, 0x1700
> [  125.741705] intel_pstate:       P2: 2200 MHz, 26297 mW, 0x1600
> [  125.741707] intel_pstate:       P3: 2000 MHz, 23263 mW, 0x1400
> [  125.741710] intel_pstate:       P4: 1900 MHz, 21924 mW, 0x1300
> [  125.741712] intel_pstate:       P5: 1800 MHz, 20612 mW, 0x1200
> [  125.741714] intel_pstate:       P6: 1600 MHz, 17812 mW, 0x1000
> [  125.741716] intel_pstate:       P7: 1500 MHz, 16581 mW, 0xf00
> [  125.741718] intel_pstate:       P8: 1300 MHz, 13946 mW, 0xd00
> [  125.741720] intel_pstate:       P9: 1200 MHz, 12796 mW, 0xc00
> [  125.741722] intel_pstate:       P10: 1100 MHz, 11426 mW, 0xb00
> [  125.741724] intel_pstate:       P11: 900 MHz, 9250 mW, 0x900
> [  125.741726] intel_pstate:       P12: 800 MHz, 7965 mW, 0x800
> [  125.741729] intel_pstate:       P13: 700 MHz, 6940 mW, 0x700
> [  125.741731] intel_pstate:       P14: 500 MHz, 4738 mW, 0x500
> [  125.741733] intel_pstate:       P15: 400 MHz, 3787 mW, 0x400
> [  125.741735] intel_pstate: _PPC limits will be enforced
> [  125.741740] intel_pstate: policy->max > max non turbo frequency
> [  125.741742] intel_pstate: cpu:1 min_policy_perf:4 max_policy_perf:42
> [  125.741745] intel_pstate: cpu:1 global_min:4 global_max:42
> [  125.741747] intel_pstate: cpu:1 max_perf_ratio:42 min_perf_ratio:4
> [  125.742243] intel_pstate: policy->max > max non turbo frequency
> [  125.742247] intel_pstate: cpu:1 min_policy_perf:4 max_policy_perf:42
> [  125.742251] intel_pstate: cpu:1 global_min:4 global_max:42
> [  125.742255] intel_pstate: cpu:1 max_perf_ratio:42 min_perf_ratio:4
>
>
> It is not clear how to get to this non turbo situation.

Look at the scaling_max_freq before and after rebooting the CPU. Before
you do it, it should be the max turbo frequency (say 2500 MHz). After
rebooting the CPU, it should now be 2301 MHz. So the kernel will now not
ask for anything above 2301 MHz, so you will never get to 2500 MHz.

Another interesting thing I observed is that if I reboot only 1 CPU, its
scaling_max_freq goes down to 2301, but it still keeps working at 2500
MHz. This might be something to do with how turbo works, I don't
understand that very well. But if you reboot say 20 CPUs, then you see
the frequency drop.

I use the below steps to reproduce this bug on my system, which has 40
CPUs with a base frequency of 2500 MHz and turbo frequency of 3300 MHz:

$ grep 'cpu MHz' /proc/cpuinfo
cpu MHz         : 3300.000
cpu MHz         : 1199.652
cpu MHz         : 3300.000
cpu MHz         : 3300.000
cpu MHz         : 3300.000
cpu MHz         : 3300.000
cpu MHz         : 3300.000
cpu MHz         : 3300.000
cpu MHz         : 3300.000
cpu MHz         : 3300.000
[ repeat 30 times ]

$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq | sort -n | uniq -c
     40 3300000
$ for i in `seq 1 20`; do echo 0 | sudo tee /sys/devices/system/cpu/cpu$i/online; done
[...]
$ for i in `seq 1 20`; do echo 1 | sudo tee /sys/devices/system/cpu/cpu$i/online; done
[...]
$ grep 'cpu MHz' /proc/cpuinfo
cpu MHz         : 3300.000
cpu MHz         : 2500.000
cpu MHz         : 2500.000
cpu MHz         : 2500.000
cpu MHz         : 2500.000
cpu MHz         : 2500.000
[ repeat 15 times ]
cpu MHz         : 3300.000
cpu MHz         : 3300.000
[ repeat 17 times ]
$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq | sort -n | uniq -c
     20 2501000
     20 3300000

>
> Thanks,
> Srinivas
>
>> Pratyush Yadav (2):
>>   acpi: processor: allow fixing up the frequency for a performance
>> state
>>   cpufreq: intel_pstate: use acpi perflib to update turbo frequency
>>
>>  drivers/acpi/processor_perflib.c | 40
>> ++++++++++++++++++++++++++++++++
>>  drivers/cpufreq/intel_pstate.c   |  5 ++--
>>  include/acpi/processor.h         |  2 ++
>>  3 files changed, 45 insertions(+), 2 deletions(-)
>>
>> --
>> 2.38.1
>>
>

-- 
Regards,
Pratyush Yadav



Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[srinivas pandruvada]

Hi Pratyush,

On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> 
> Hi Srinivas,
> 
> On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> > > When a processor is brought offline and online again, it is
> > > unable to
> > > use Turbo mode because the _PSS table does not contain the whole
> > > turbo
> > > frequency range, but only +1 MHz above the max non-turbo
> > > frequency.
> > > This
> > > causes problems when ACPI processor driver tries to set frequency
> > > constraints. See patch 2 for more details.
> > > 
I can reproduce on a Broadwell server platform. But not on a client
system with acpi_ppc usage.

Need to check what change broke this.

Thanks,
Srinivas

> > 
> > Thanks,
> > Srinivas
> > 
> > > Pratyush Yadav (2):
> > >   acpi: processor: allow fixing up the frequency for a
> > > performance
> > > state
> > >   cpufreq: intel_pstate: use acpi perflib to update turbo
> > > frequency
> > > 
> > >  drivers/acpi/processor_perflib.c | 40
> > > ++++++++++++++++++++++++++++++++
> > >  drivers/cpufreq/intel_pstate.c   |  5 ++--
> > >  include/acpi/processor.h         |  2 ++
> > >  3 files changed, 45 insertions(+), 2 deletions(-)
> > > 
> > > --
> > > 2.38.1
> > > 
> > 
> 

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[srinivas pandruvada]

On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
> Hi Pratyush,
> 
> On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> > 
> > Hi Srinivas,
> > 
> > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> > > > When a processor is brought offline and online again, it is
> > > > unable to
> > > > use Turbo mode because the _PSS table does not contain the whole
> > > > turbo
> > > > frequency range, but only +1 MHz above the max non-turbo
> > > > frequency.
> > > > This
> > > > causes problems when ACPI processor driver tries to set frequency
> > > > constraints. See patch 2 for more details.
> > > > 
> I can reproduce on a Broadwell server platform. But not on a client
> system with acpi_ppc usage.
> 
> Need to check what change broke this.

When PPC limits enforcement changed to PM QOS, this broke. Previously
acpi_processor_get_platform_limit() was not enforcing any limits. It
was just setting variable. So any update done after
acpi_register_performance_state() call to pr->performance-
>states[ppc].core_frequency, was effective.

We don't really need to call
	ret = freq_qos_update_request(&pr->perflib_req,
			pr->performance->states[ppc].core_frequency *
1000);

if the PPC is not changed. When PPC is changed, this gets called again,
so then we can call the above function to update cpufreq limit.

The below change fixed for me.

diff --git a/drivers/acpi/processor_perflib.c
b/drivers/acpi/processor_perflib.c
index 757a98f6d7a2..c6ced89c00dd 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -75,6 +75,11 @@ static int acpi_processor_get_platform_limit(struct
acpi_processor *pr)
        pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr->id,
                       (int)ppc, ppc ? "" : "not");
 
+       if (ppc == pr->performance_platform_limit) {
+               pr_debug("CPU %d: _PPC is %d - frequency not
changed\n", pr->id, ppc);
+               return 0;
+       }
+
        pr->performance_platform_limit = (int)ppc;
 
        if (ppc >= pr->performance->state_count ||

Thanks,
Srinivas

> 
> Thanks,
> Srinivas
> 
> > > 
> > > Thanks,
> > > Srinivas
> > > 
> > > > Pratyush Yadav (2):
> > > >   acpi: processor: allow fixing up the frequency for a
> > > > performance
> > > > state
> > > >   cpufreq: intel_pstate: use acpi perflib to update turbo
> > > > frequency
> > > > 
> > > >  drivers/acpi/processor_perflib.c | 40
> > > > ++++++++++++++++++++++++++++++++
> > > >  drivers/cpufreq/intel_pstate.c   |  5 ++--
> > > >  include/acpi/processor.h         |  2 ++
> > > >  3 files changed, 45 insertions(+), 2 deletions(-)
> > > > 
> > > > --
> > > > 2.38.1
> > > > 
> > > 
> > 
> 

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Pratyush Yadav]

Hi Srinivas,

On Sat, Dec 24 2022, srinivas pandruvada wrote:

> On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
>> Hi Pratyush,
>>
>> On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
>> >
>> > Hi Srinivas,
>> >
>> > On Wed, Dec 21 2022, srinivas pandruvada wrote:
>> > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
>> > > > When a processor is brought offline and online again, it is
>> > > > unable to
>> > > > use Turbo mode because the _PSS table does not contain the whole
>> > > > turbo
>> > > > frequency range, but only +1 MHz above the max non-turbo
>> > > > frequency.
>> > > > This
>> > > > causes problems when ACPI processor driver tries to set frequency
>> > > > constraints. See patch 2 for more details.
>> > > >
>> I can reproduce on a Broadwell server platform. But not on a client
>> system with acpi_ppc usage.
>>
>> Need to check what change broke this.
>
> When PPC limits enforcement changed to PM QOS, this broke. Previously
> acpi_processor_get_platform_limit() was not enforcing any limits. It
> was just setting variable. So any update done after
> acpi_register_performance_state() call to pr->performance-
>>states[ppc].core_frequency, was effective.
>
> We don't really need to call
>         ret = freq_qos_update_request(&pr->perflib_req,
>                         pr->performance->states[ppc].core_frequency *
> 1000);
>
> if the PPC is not changed. When PPC is changed, this gets called again,
> so then we can call the above function to update cpufreq limit.
>
> The below change fixed for me.

Right. Should I re-roll my patches with your diff below then? Or do you
think my patches should be good to merge as-is?

>
> diff --git a/drivers/acpi/processor_perflib.c
> b/drivers/acpi/processor_perflib.c
> index 757a98f6d7a2..c6ced89c00dd 100644
> --- a/drivers/acpi/processor_perflib.c
> +++ b/drivers/acpi/processor_perflib.c
> @@ -75,6 +75,11 @@ static int acpi_processor_get_platform_limit(struct
> acpi_processor *pr)
>         pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr->id,
>                        (int)ppc, ppc ? "" : "not");
>
> +       if (ppc == pr->performance_platform_limit) {
> +               pr_debug("CPU %d: _PPC is %d - frequency not
> changed\n", pr->id, ppc);
> +               return 0;
> +       }
> +
>         pr->performance_platform_limit = (int)ppc;
>
>         if (ppc >= pr->performance->state_count ||
>

-- 
Regards,
Pratyush Yadav



Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Rafael J. Wysocki]

On Tue, Dec 27, 2022 at 4:38 PM Pratyush Yadav <ptyadav@amazon.de> wrote:
>
> Hi Srinivas,
>
> On Sat, Dec 24 2022, srinivas pandruvada wrote:
>
> > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
> >> Hi Pratyush,
> >>
> >> On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> >> >
> >> > Hi Srinivas,
> >> >
> >> > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> >> > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> >> > > > When a processor is brought offline and online again, it is
> >> > > > unable to
> >> > > > use Turbo mode because the _PSS table does not contain the whole
> >> > > > turbo
> >> > > > frequency range, but only +1 MHz above the max non-turbo
> >> > > > frequency.
> >> > > > This
> >> > > > causes problems when ACPI processor driver tries to set frequency
> >> > > > constraints. See patch 2 for more details.
> >> > > >
> >> I can reproduce on a Broadwell server platform. But not on a client
> >> system with acpi_ppc usage.
> >>
> >> Need to check what change broke this.
> >
> > When PPC limits enforcement changed to PM QOS, this broke. Previously
> > acpi_processor_get_platform_limit() was not enforcing any limits. It
> > was just setting variable. So any update done after
> > acpi_register_performance_state() call to pr->performance-
> >>states[ppc].core_frequency, was effective.
> >
> > We don't really need to call
> >         ret = freq_qos_update_request(&pr->perflib_req,
> >                         pr->performance->states[ppc].core_frequency *
> > 1000);
> >
> > if the PPC is not changed. When PPC is changed, this gets called again,
> > so then we can call the above function to update cpufreq limit.
> >
> > The below change fixed for me.
>
> Right. Should I re-roll my patches with your diff below then? Or do you
> think my patches should be good to merge as-is?

No, they are not good to merge.

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[srinivas pandruvada]

On Tue, 2022-12-27 at 16:38 +0100, Pratyush Yadav wrote:
> Hi Srinivas,
> 
> On Sat, Dec 24 2022, srinivas pandruvada wrote:
> 
> > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
> > > Hi Pratyush,
> > > 
> > > On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> > > > 
> > > > Hi Srinivas,
> > > > 
> > > > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > > > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> > > > > > When a processor is brought offline and online again, it is
> > > > > > unable to
> > > > > > use Turbo mode because the _PSS table does not contain the
> > > > > > whole
> > > > > > turbo
> > > > > > frequency range, but only +1 MHz above the max non-turbo
> > > > > > frequency.
> > > > > > This
> > > > > > causes problems when ACPI processor driver tries to set
> > > > > > frequency
> > > > > > constraints. See patch 2 for more details.
> > > > > > 
> > > I can reproduce on a Broadwell server platform. But not on a
> > > client
> > > system with acpi_ppc usage.
> > > 
> > > Need to check what change broke this.
> > 
> > When PPC limits enforcement changed to PM QOS, this broke.
> > Previously
> > acpi_processor_get_platform_limit() was not enforcing any limits.
> > It
> > was just setting variable. So any update done after
> > acpi_register_performance_state() call to pr->performance-
> > > states[ppc].core_frequency, was effective.
> > 
> > We don't really need to call
> >         ret = freq_qos_update_request(&pr->perflib_req,
> >                         pr->performance->states[ppc].core_frequency
> > *
> > 1000);
> > 
> > if the PPC is not changed. When PPC is changed, this gets called
> > again,
> > so then we can call the above function to update cpufreq limit.
> > 
> > The below change fixed for me.
> 
> Right. 
I think, this is the only change you require to fix this. In addition
set pr->performance_platform_limit = 0 in
acpi_processor_unregister_performance().

Thanks,
Srinivas

> Should I re-roll my patches with your diff below then? Or do you
> think my patches should be good to merge as-is?
> 
> > 
> > diff --git a/drivers/acpi/processor_perflib.c
> > b/drivers/acpi/processor_perflib.c
> > index 757a98f6d7a2..c6ced89c00dd 100644
> > --- a/drivers/acpi/processor_perflib.c
> > +++ b/drivers/acpi/processor_perflib.c
> > @@ -75,6 +75,11 @@ static int
> > acpi_processor_get_platform_limit(struct
> > acpi_processor *pr)
> >         pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr-
> > >id,
> >                        (int)ppc, ppc ? "" : "not");
> > 
> > +       if (ppc == pr->performance_platform_limit) {
> > +               pr_debug("CPU %d: _PPC is %d - frequency not
> > changed\n", pr->id, ppc);
> > +               return 0;
> > +       }
> > +
> >         pr->performance_platform_limit = (int)ppc;
> > 
> >         if (ppc >= pr->performance->state_count ||
> > 
> 

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Rafael J. Wysocki]

On Tue, Dec 27, 2022 at 5:40 PM srinivas pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
>
> On Tue, 2022-12-27 at 16:38 +0100, Pratyush Yadav wrote:
> > Hi Srinivas,
> >
> > On Sat, Dec 24 2022, srinivas pandruvada wrote:
> >
> > > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
> > > > Hi Pratyush,
> > > >
> > > > On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> > > > >
> > > > > Hi Srinivas,
> > > > >
> > > > > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > > > > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> > > > > > > When a processor is brought offline and online again, it is
> > > > > > > unable to
> > > > > > > use Turbo mode because the _PSS table does not contain the
> > > > > > > whole
> > > > > > > turbo
> > > > > > > frequency range, but only +1 MHz above the max non-turbo
> > > > > > > frequency.
> > > > > > > This
> > > > > > > causes problems when ACPI processor driver tries to set
> > > > > > > frequency
> > > > > > > constraints. See patch 2 for more details.
> > > > > > >
> > > > I can reproduce on a Broadwell server platform. But not on a
> > > > client
> > > > system with acpi_ppc usage.
> > > >
> > > > Need to check what change broke this.
> > >
> > > When PPC limits enforcement changed to PM QOS, this broke.
> > > Previously
> > > acpi_processor_get_platform_limit() was not enforcing any limits.
> > > It
> > > was just setting variable. So any update done after
> > > acpi_register_performance_state() call to pr->performance-
> > > > states[ppc].core_frequency, was effective.
> > >
> > > We don't really need to call
> > >         ret = freq_qos_update_request(&pr->perflib_req,
> > >                         pr->performance->states[ppc].core_frequency
> > > *
> > > 1000);
> > >
> > > if the PPC is not changed. When PPC is changed, this gets called
> > > again,
> > > so then we can call the above function to update cpufreq limit.
> > >
> > > The below change fixed for me.
> >
> > Right.
> I think, this is the only change you require to fix this. In addition
> set pr->performance_platform_limit = 0 in
> acpi_processor_unregister_performance().

Not really, because if the limit is set to a lower frequency and then
reset to _PSS[0], it needs to be set back to "no limit".

I'll send a patch for that in a while.

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Rafael J. Wysocki]

On Tuesday, December 27, 2022 6:02:50 PM CET Rafael J. Wysocki wrote:
> On Tue, Dec 27, 2022 at 5:40 PM srinivas pandruvada
> <srinivas.pandruvada@linux.intel.com> wrote:
> >
> > On Tue, 2022-12-27 at 16:38 +0100, Pratyush Yadav wrote:
> > > Hi Srinivas,
> > >
> > > On Sat, Dec 24 2022, srinivas pandruvada wrote:
> > >
> > > > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
> > > > > Hi Pratyush,
> > > > >
> > > > > On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> > > > > >
> > > > > > Hi Srinivas,
> > > > > >
> > > > > > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > > > > > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> > > > > > > > When a processor is brought offline and online again, it is
> > > > > > > > unable to
> > > > > > > > use Turbo mode because the _PSS table does not contain the
> > > > > > > > whole
> > > > > > > > turbo
> > > > > > > > frequency range, but only +1 MHz above the max non-turbo
> > > > > > > > frequency.
> > > > > > > > This
> > > > > > > > causes problems when ACPI processor driver tries to set
> > > > > > > > frequency
> > > > > > > > constraints. See patch 2 for more details.
> > > > > > > >
> > > > > I can reproduce on a Broadwell server platform. But not on a
> > > > > client
> > > > > system with acpi_ppc usage.
> > > > >
> > > > > Need to check what change broke this.
> > > >
> > > > When PPC limits enforcement changed to PM QOS, this broke.
> > > > Previously
> > > > acpi_processor_get_platform_limit() was not enforcing any limits.
> > > > It
> > > > was just setting variable. So any update done after
> > > > acpi_register_performance_state() call to pr->performance-
> > > > > states[ppc].core_frequency, was effective.
> > > >
> > > > We don't really need to call
> > > >         ret = freq_qos_update_request(&pr->perflib_req,
> > > >                         pr->performance->states[ppc].core_frequency
> > > > *
> > > > 1000);
> > > >
> > > > if the PPC is not changed. When PPC is changed, this gets called
> > > > again,
> > > > so then we can call the above function to update cpufreq limit.
> > > >
> > > > The below change fixed for me.
> > >
> > > Right.
> > I think, this is the only change you require to fix this. In addition
> > set pr->performance_platform_limit = 0 in
> > acpi_processor_unregister_performance().
> 
> Not really, because if the limit is set to a lower frequency and then
> reset to _PSS[0], it needs to be set back to "no limit".
> 
> I'll send a patch for that in a while.

This has not been tested beyond compilation, so please be careful.

---
 drivers/acpi/processor_perflib.c |   27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

Index: linux-pm/drivers/acpi/processor_perflib.c
===================================================================
--- linux-pm.orig/drivers/acpi/processor_perflib.c
+++ linux-pm/drivers/acpi/processor_perflib.c
@@ -53,6 +53,8 @@ static int acpi_processor_get_platform_l
 {
 	acpi_status status = 0;
 	unsigned long long ppc = 0;
+	s32 qos_value;
+	int index;
 	int ret;
 
 	if (!pr)
@@ -72,17 +74,30 @@ static int acpi_processor_get_platform_l
 		}
 	}
 
+	index = ppc;
+
+	if (pr->performance_platform_limit == index ||
+	    ppc >= pr->performance->state_count)
+		return 0;
+
 	pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr->id,
-		       (int)ppc, ppc ? "" : "not");
+		 index, index ? "is" : "is not");
 
-	pr->performance_platform_limit = (int)ppc;
+	pr->performance_platform_limit = index;
 
-	if (ppc >= pr->performance->state_count ||
-	    unlikely(!freq_qos_request_active(&pr->perflib_req)))
+	if (unlikely(!freq_qos_request_active(&pr->perflib_req)))
 		return 0;
 
-	ret = freq_qos_update_request(&pr->perflib_req,
-			pr->performance->states[ppc].core_frequency * 1000);
+	/*
+	 * If _PPC returns 0, it means that all of the available states can be
+	 * used ("no limit").
+	 */
+	if (index == 0)
+		qos_value = FREQ_QOS_MAX_DEFAULT_VALUE;
+	else
+		qos_value = pr->performance->states[index].core_frequency * 1000;
+
+	ret = freq_qos_update_request(&pr->perflib_req, qos_value);
 	if (ret < 0) {
 		pr_warn("Failed to update perflib freq constraint: CPU%d (%d)\n",
 			pr->id, ret);

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[srinivas pandruvada]

On Tue, 2022-12-27 at 18:02 +0100, Rafael J. Wysocki wrote:
> On Tue, Dec 27, 2022 at 5:40 PM srinivas pandruvada
> <srinivas.pandruvada@linux.intel.com> wrote:
> > 
> > On Tue, 2022-12-27 at 16:38 +0100, Pratyush Yadav wrote:
> > > Hi Srinivas,
> > > 
> > > On Sat, Dec 24 2022, srinivas pandruvada wrote:
> > > 
> > > > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
> > > > > Hi Pratyush,
> > > > > 
> > > > > On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> > > > > > 
> > > > > > Hi Srinivas,
> > > > > > 
> > > > > > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > > > > > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> > > > > > > > When a processor is brought offline and online again,
> > > > > > > > it is
> > > > > > > > unable to
> > > > > > > > use Turbo mode because the _PSS table does not contain
> > > > > > > > the
> > > > > > > > whole
> > > > > > > > turbo
> > > > > > > > frequency range, but only +1 MHz above the max non-
> > > > > > > > turbo
> > > > > > > > frequency.
> > > > > > > > This
> > > > > > > > causes problems when ACPI processor driver tries to set
> > > > > > > > frequency
> > > > > > > > constraints. See patch 2 for more details.
> > > > > > > > 
> > > > > I can reproduce on a Broadwell server platform. But not on a
> > > > > client
> > > > > system with acpi_ppc usage.
> > > > > 
> > > > > Need to check what change broke this.
> > > > 
> > > > When PPC limits enforcement changed to PM QOS, this broke.
> > > > Previously
> > > > acpi_processor_get_platform_limit() was not enforcing any
> > > > limits.
> > > > It
> > > > was just setting variable. So any update done after
> > > > acpi_register_performance_state() call to pr->performance-
> > > > > states[ppc].core_frequency, was effective.
> > > > 
> > > > We don't really need to call
> > > >         ret = freq_qos_update_request(&pr->perflib_req,
> > > >                         pr->performance-
> > > > >states[ppc].core_frequency
> > > > *
> > > > 1000);
> > > > 
> > > > if the PPC is not changed. When PPC is changed, this gets
> > > > called
> > > > again,
> > > > so then we can call the above function to update cpufreq limit.
> > > > 
> > > > The below change fixed for me.
> > > 
> > > Right.
> > I think, this is the only change you require to fix this. In
> > addition
> > set pr->performance_platform_limit = 0 in
> > acpi_processor_unregister_performance().
> 
> Not really, because if the limit is set to a lower frequency and then
> reset to _PSS[0], it needs to be set back to "no limit".
> 

If PPC becomes 0 again after ppc > 0 during dynamic PPC change, pr-
>performance_platform_limit will not match current PPC, so will set to
PPC 0 performance ( which is already patched by driver after return
from acpi_register_performance_state()).

But fine, you can always set freq qos to FREQ_QOS_MAX_DEFAULT_VALUE for
PPC 0 as you are doing in your patch.

Thanks,
Srinivas




> I'll send a patch for that in a while.

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Rafael J. Wysocki]

On Tue, Dec 27, 2022 at 7:07 PM srinivas pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
>
> On Tue, 2022-12-27 at 18:02 +0100, Rafael J. Wysocki wrote:
> > On Tue, Dec 27, 2022 at 5:40 PM srinivas pandruvada
> > <srinivas.pandruvada@linux.intel.com> wrote:
> > >
> > > On Tue, 2022-12-27 at 16:38 +0100, Pratyush Yadav wrote:
> > > > Hi Srinivas,
> > > >
> > > > On Sat, Dec 24 2022, srinivas pandruvada wrote:
> > > >
> > > > > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada wrote:
> > > > > > Hi Pratyush,
> > > > > >
> > > > > > On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> > > > > > >
> > > > > > > Hi Srinivas,
> > > > > > >
> > > > > > > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > > > > > > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav wrote:
> > > > > > > > > When a processor is brought offline and online again,
> > > > > > > > > it is
> > > > > > > > > unable to
> > > > > > > > > use Turbo mode because the _PSS table does not contain
> > > > > > > > > the
> > > > > > > > > whole
> > > > > > > > > turbo
> > > > > > > > > frequency range, but only +1 MHz above the max non-
> > > > > > > > > turbo
> > > > > > > > > frequency.
> > > > > > > > > This
> > > > > > > > > causes problems when ACPI processor driver tries to set
> > > > > > > > > frequency
> > > > > > > > > constraints. See patch 2 for more details.
> > > > > > > > >
> > > > > > I can reproduce on a Broadwell server platform. But not on a
> > > > > > client
> > > > > > system with acpi_ppc usage.
> > > > > >
> > > > > > Need to check what change broke this.
> > > > >
> > > > > When PPC limits enforcement changed to PM QOS, this broke.
> > > > > Previously
> > > > > acpi_processor_get_platform_limit() was not enforcing any
> > > > > limits.
> > > > > It
> > > > > was just setting variable. So any update done after
> > > > > acpi_register_performance_state() call to pr->performance-
> > > > > > states[ppc].core_frequency, was effective.
> > > > >
> > > > > We don't really need to call
> > > > >         ret = freq_qos_update_request(&pr->perflib_req,
> > > > >                         pr->performance-
> > > > > >states[ppc].core_frequency
> > > > > *
> > > > > 1000);
> > > > >
> > > > > if the PPC is not changed. When PPC is changed, this gets
> > > > > called
> > > > > again,
> > > > > so then we can call the above function to update cpufreq limit.
> > > > >
> > > > > The below change fixed for me.
> > > >
> > > > Right.
> > > I think, this is the only change you require to fix this. In
> > > addition
> > > set pr->performance_platform_limit = 0 in
> > > acpi_processor_unregister_performance().
> >
> > Not really, because if the limit is set to a lower frequency and then
> > reset to _PSS[0], it needs to be set back to "no limit".
> >
>
> If PPC becomes 0 again after ppc > 0 during dynamic PPC change, pr-
> >performance_platform_limit will not match current PPC, so will set to
> PPC 0 performance ( which is already patched by driver after return
> from acpi_register_performance_state()).

I see.

> But fine, you can always set freq qos to FREQ_QOS_MAX_DEFAULT_VALUE for
> PPC 0 as you are doing in your patch.

I think that using the "no limit" value to represent the "no limit"
condition makes sense.

Also, I'm wondering if the patching of states[0].core_frequency will
still be necessary after this change.

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[srinivas pandruvada]

On Tue, 2022-12-27 at 19:47 +0100, Rafael J. Wysocki wrote:
> On Tue, Dec 27, 2022 at 7:07 PM srinivas pandruvada
> <srinivas.pandruvada@linux.intel.com> wrote:
> > 
> > On Tue, 2022-12-27 at 18:02 +0100, Rafael J. Wysocki wrote:
> > > On Tue, Dec 27, 2022 at 5:40 PM srinivas pandruvada
> > > <srinivas.pandruvada@linux.intel.com> wrote:
> > > > 
> > > > On Tue, 2022-12-27 at 16:38 +0100, Pratyush Yadav wrote:
> > > > > Hi Srinivas,
> > > > > 
> > > > > On Sat, Dec 24 2022, srinivas pandruvada wrote:
> > > > > 
> > > > > > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada
> > > > > > wrote:
> > > > > > > Hi Pratyush,
> > > > > > > 
> > > > > > > On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> > > > > > > > 
> > > > > > > > Hi Srinivas,
> > > > > > > > 
> > > > > > > > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > > > > > > > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav
> > > > > > > > > wrote:
> > > > > > > > > > When a processor is brought offline and online
> > > > > > > > > > again,
> > > > > > > > > > it is
> > > > > > > > > > unable to
> > > > > > > > > > use Turbo mode because the _PSS table does not
> > > > > > > > > > contain
> > > > > > > > > > the
> > > > > > > > > > whole
> > > > > > > > > > turbo
> > > > > > > > > > frequency range, but only +1 MHz above the max non-
> > > > > > > > > > turbo
> > > > > > > > > > frequency.
> > > > > > > > > > This
> > > > > > > > > > causes problems when ACPI processor driver tries to
> > > > > > > > > > set
> > > > > > > > > > frequency
> > > > > > > > > > constraints. See patch 2 for more details.
> > > > > > > > > > 
> > > > > > > I can reproduce on a Broadwell server platform. But not
> > > > > > > on a
> > > > > > > client
> > > > > > > system with acpi_ppc usage.
> > > > > > > 
> > > > > > > Need to check what change broke this.
> > > > > > 
> > > > > > When PPC limits enforcement changed to PM QOS, this broke.
> > > > > > Previously
> > > > > > acpi_processor_get_platform_limit() was not enforcing any
> > > > > > limits.
> > > > > > It
> > > > > > was just setting variable. So any update done after
> > > > > > acpi_register_performance_state() call to pr->performance-
> > > > > > > states[ppc].core_frequency, was effective.
> > > > > > 
> > > > > > We don't really need to call
> > > > > >         ret = freq_qos_update_request(&pr->perflib_req,
> > > > > >                         pr->performance-
> > > > > > > states[ppc].core_frequency
> > > > > > *
> > > > > > 1000);
> > > > > > 
> > > > > > if the PPC is not changed. When PPC is changed, this gets
> > > > > > called
> > > > > > again,
> > > > > > so then we can call the above function to update cpufreq
> > > > > > limit.
> > > > > > 
> > > > > > The below change fixed for me.
> > > > > 
> > > > > Right.
> > > > I think, this is the only change you require to fix this. In
> > > > addition
> > > > set pr->performance_platform_limit = 0 in
> > > > acpi_processor_unregister_performance().
> > > 
> > > Not really, because if the limit is set to a lower frequency and
> > > then
> > > reset to _PSS[0], it needs to be set back to "no limit".
> > > 
> > 
> > If PPC becomes 0 again after ppc > 0 during dynamic PPC change, pr-
> > > performance_platform_limit will not match current PPC, so will
> > > set to
> > PPC 0 performance ( which is already patched by driver after return
> > from acpi_register_performance_state()).
> 
> I see.
> 
> > But fine, you can always set freq qos to FREQ_QOS_MAX_DEFAULT_VALUE
> > for
> > PPC 0 as you are doing in your patch.
> 
> I think that using the "no limit" value to represent the "no limit"
> condition makes sense.
Agree.

> 
> Also, I'm wondering if the patching of states[0].core_frequency will
> still be necessary after this change.

I don't think so. We can remove the patching.

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Rafael J. Wysocki]

On Tue, Dec 27, 2022 at 7:49 PM srinivas pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
>
> On Tue, 2022-12-27 at 19:47 +0100, Rafael J. Wysocki wrote:
> > On Tue, Dec 27, 2022 at 7:07 PM srinivas pandruvada
> > <srinivas.pandruvada@linux.intel.com> wrote:
> > >
> > > On Tue, 2022-12-27 at 18:02 +0100, Rafael J. Wysocki wrote:
> > > > On Tue, Dec 27, 2022 at 5:40 PM srinivas pandruvada
> > > > <srinivas.pandruvada@linux.intel.com> wrote:
> > > > >
> > > > > On Tue, 2022-12-27 at 16:38 +0100, Pratyush Yadav wrote:
> > > > > > Hi Srinivas,
> > > > > >
> > > > > > On Sat, Dec 24 2022, srinivas pandruvada wrote:
> > > > > >
> > > > > > > On Fri, 2022-12-23 at 10:10 -0800, srinivas pandruvada
> > > > > > > wrote:
> > > > > > > > Hi Pratyush,
> > > > > > > >
> > > > > > > > On Thu, 2022-12-22 at 11:39 +0100, Pratyush Yadav wrote:
> > > > > > > > >
> > > > > > > > > Hi Srinivas,
> > > > > > > > >
> > > > > > > > > On Wed, Dec 21 2022, srinivas pandruvada wrote:
> > > > > > > > > > On Wed, 2022-12-21 at 16:52 +0100, Pratyush Yadav
> > > > > > > > > > wrote:
> > > > > > > > > > > When a processor is brought offline and online
> > > > > > > > > > > again,
> > > > > > > > > > > it is
> > > > > > > > > > > unable to
> > > > > > > > > > > use Turbo mode because the _PSS table does not
> > > > > > > > > > > contain
> > > > > > > > > > > the
> > > > > > > > > > > whole
> > > > > > > > > > > turbo
> > > > > > > > > > > frequency range, but only +1 MHz above the max non-
> > > > > > > > > > > turbo
> > > > > > > > > > > frequency.
> > > > > > > > > > > This
> > > > > > > > > > > causes problems when ACPI processor driver tries to
> > > > > > > > > > > set
> > > > > > > > > > > frequency
> > > > > > > > > > > constraints. See patch 2 for more details.
> > > > > > > > > > >
> > > > > > > > I can reproduce on a Broadwell server platform. But not
> > > > > > > > on a
> > > > > > > > client
> > > > > > > > system with acpi_ppc usage.
> > > > > > > >
> > > > > > > > Need to check what change broke this.
> > > > > > >
> > > > > > > When PPC limits enforcement changed to PM QOS, this broke.
> > > > > > > Previously
> > > > > > > acpi_processor_get_platform_limit() was not enforcing any
> > > > > > > limits.
> > > > > > > It
> > > > > > > was just setting variable. So any update done after
> > > > > > > acpi_register_performance_state() call to pr->performance-
> > > > > > > > states[ppc].core_frequency, was effective.
> > > > > > >
> > > > > > > We don't really need to call
> > > > > > >         ret = freq_qos_update_request(&pr->perflib_req,
> > > > > > >                         pr->performance-
> > > > > > > > states[ppc].core_frequency
> > > > > > > *
> > > > > > > 1000);
> > > > > > >
> > > > > > > if the PPC is not changed. When PPC is changed, this gets
> > > > > > > called
> > > > > > > again,
> > > > > > > so then we can call the above function to update cpufreq
> > > > > > > limit.
> > > > > > >
> > > > > > > The below change fixed for me.
> > > > > >
> > > > > > Right.
> > > > > I think, this is the only change you require to fix this. In
> > > > > addition
> > > > > set pr->performance_platform_limit = 0 in
> > > > > acpi_processor_unregister_performance().
> > > >
> > > > Not really, because if the limit is set to a lower frequency and
> > > > then
> > > > reset to _PSS[0], it needs to be set back to "no limit".
> > > >
> > >
> > > If PPC becomes 0 again after ppc > 0 during dynamic PPC change, pr-
> > > > performance_platform_limit will not match current PPC, so will
> > > > set to
> > > PPC 0 performance ( which is already patched by driver after return
> > > from acpi_register_performance_state()).
> >
> > I see.
> >
> > > But fine, you can always set freq qos to FREQ_QOS_MAX_DEFAULT_VALUE
> > > for
> > > PPC 0 as you are doing in your patch.
> >
> > I think that using the "no limit" value to represent the "no limit"
> > condition makes sense.
> Agree.
>
> >
> > Also, I'm wondering if the patching of states[0].core_frequency will
> > still be necessary after this change.
>
> I don't think so. We can remove the patching.

OK, let me cut the patches.

Re: [PATCH 0/2] intel_pstate: fix turbo not being used after a processor is rebooted

[Rafael J. Wysocki]

On Wed, Dec 21, 2022 at 4:52 PM Pratyush Yadav <ptyadav@amazon.de> wrote:
>
> When a processor is brought offline and online again, it is unable to
> use Turbo mode because the _PSS table does not contain the whole turbo
> frequency range, but only +1 MHz above the max non-turbo frequency.

That's because of the way P-state limits in the turbo range are
handled by the given processor.

Some of them restrict the P-state even if the limit is located within
the turbo range and some of them don't (that is, requesting any
P-state in the turbo range gives the processor a license to use the
whole of it).

> This causes problems when ACPI processor driver tries to set frequency
> constraints.

The problem is that acpi_processor_get_platform_limit() sets the limit
to the frequency for all of the _PSS states including the last special
one and it should update the QoS to "no limit" in that case.