[PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Pengjie Zhang]

The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
linear performance scaling. Performance levels below this threshold
are typically inefficient and should not be used by default.

Currently, the QoS minimum request is initialized to 0. This defaults
the performance floor to the absolute "Lowest Performance" state
instead of "lowest_nonlinear_perf", allowing the CPU to operate in
an inefficient range unnecessarily.

Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
---
Changes in v2:
  - Renamed the patch subject to better reflect the logic change.
  - Updated the commit log to clarify ACPI spec details.
Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
---
 drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 7e8042efedd1..4a3031d9fcf4 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
 	return target_freq;
 }
 
-static int cppc_verify_policy(struct cpufreq_policy_data *policy)
+static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
 {
-	cpufreq_verify_within_cpu_limits(policy);
+	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
+		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
+					      cpufreq_cpu_get(policy_data->cpu);
+		struct cppc_cpudata *cpu_data;
+
+		if (!policy)
+			return -EINVAL;
+
+		cpu_data = policy->driver_data;
+		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
+			cpu_data->perf_caps.lowest_nonlinear_perf);
+	}
+
+	cpufreq_verify_within_cpu_limits(policy_data);
+
 	return 0;
 }
 
-- 
2.33.0

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[zhangpengjie (A)]

Just a gentle ping on this patch.
Thanks, Pengjie

On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
> linear performance scaling. Performance levels below this threshold
> are typically inefficient and should not be used by default.
>
> Currently, the QoS minimum request is initialized to 0. This defaults
> the performance floor to the absolute "Lowest Performance" state
> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
> an inefficient range unnecessarily.
>
> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> ---
> Changes in v2:
>    - Renamed the patch subject to better reflect the logic change.
>    - Updated the commit log to clarify ACPI spec details.
> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
> ---
>   drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>   1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 7e8042efedd1..4a3031d9fcf4 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>   	return target_freq;
>   }
>   
> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>   {
> -	cpufreq_verify_within_cpu_limits(policy);
> +	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
> +		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
> +					      cpufreq_cpu_get(policy_data->cpu);
> +		struct cppc_cpudata *cpu_data;
> +
> +		if (!policy)
> +			return -EINVAL;
> +
> +		cpu_data = policy->driver_data;
> +		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
> +			cpu_data->perf_caps.lowest_nonlinear_perf);
> +	}
> +
> +	cpufreq_verify_within_cpu_limits(policy_data);
> +
>   	return 0;
>   }
>   

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Viresh Kumar]

Added few more people

I think we should updated MAINTAINERS with a list of reviewers or maintainers
for the CPPC driver. Who all want to be part of the reviewers list ?

On 03-03-26, 20:03, zhangpengjie (A) wrote:
> Just a gentle ping on this patch.
> Thanks, Pengjie
> 
> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
> > The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
> > linear performance scaling. Performance levels below this threshold
> > are typically inefficient and should not be used by default.
> > 
> > Currently, the QoS minimum request is initialized to 0. This defaults
> > the performance floor to the absolute "Lowest Performance" state
> > instead of "lowest_nonlinear_perf", allowing the CPU to operate in
> > an inefficient range unnecessarily.
> > 
> > Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> > ---
> > Changes in v2:
> >    - Renamed the patch subject to better reflect the logic change.
> >    - Updated the commit log to clarify ACPI spec details.
> > Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
> > ---
> >   drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
> >   1 file changed, 16 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> > index 7e8042efedd1..4a3031d9fcf4 100644
> > --- a/drivers/cpufreq/cppc_cpufreq.c
> > +++ b/drivers/cpufreq/cppc_cpufreq.c
> > @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
> >   	return target_freq;
> >   }
> > -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
> > +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
> >   {
> > -	cpufreq_verify_within_cpu_limits(policy);
> > +	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
> > +		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
> > +					      cpufreq_cpu_get(policy_data->cpu);
> > +		struct cppc_cpudata *cpu_data;
> > +
> > +		if (!policy)
> > +			return -EINVAL;
> > +
> > +		cpu_data = policy->driver_data;
> > +		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
> > +			cpu_data->perf_caps.lowest_nonlinear_perf);
> > +	}
> > +
> > +	cpufreq_verify_within_cpu_limits(policy_data);
> > +
> >   	return 0;
> >   }

-- 
viresh

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Jie Zhan]

Hi Viresh,

I'm happy with rewiewing or maintaining this.
We're consistently using the CPPC cpufreq driver for our SoCs.

BTW, will take a look at Pengjie's patches soon!

Thanks,
Jie

On 3/5/2026 2:32 PM, Viresh Kumar wrote:
> Added few more people
> 
> I think we should updated MAINTAINERS with a list of reviewers or maintainers
> for the CPPC driver. Who all want to be part of the reviewers list ?
> 
> On 03-03-26, 20:03, zhangpengjie (A) wrote:
>> Just a gentle ping on this patch.
>> Thanks, Pengjie
>>
>> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
>>> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
>>> linear performance scaling. Performance levels below this threshold
>>> are typically inefficient and should not be used by default.
>>>
>>> Currently, the QoS minimum request is initialized to 0. This defaults
>>> the performance floor to the absolute "Lowest Performance" state
>>> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
>>> an inefficient range unnecessarily.
>>>
>>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
>>> ---
>>> Changes in v2:
>>>    - Renamed the patch subject to better reflect the logic change.
>>>    - Updated the commit log to clarify ACPI spec details.
>>> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
>>> ---
>>>   drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>>>   1 file changed, 16 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>>> index 7e8042efedd1..4a3031d9fcf4 100644
>>> --- a/drivers/cpufreq/cppc_cpufreq.c
>>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>>> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>>>   	return target_freq;
>>>   }
>>> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
>>> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>>>   {
>>> -	cpufreq_verify_within_cpu_limits(policy);
>>> +	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
>>> +		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>>> +					      cpufreq_cpu_get(policy_data->cpu);
>>> +		struct cppc_cpudata *cpu_data;
>>> +
>>> +		if (!policy)
>>> +			return -EINVAL;
>>> +
>>> +		cpu_data = policy->driver_data;
>>> +		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
>>> +			cpu_data->perf_caps.lowest_nonlinear_perf);
>>> +	}
>>> +
>>> +	cpufreq_verify_within_cpu_limits(policy_data);
>>> +
>>>   	return 0;
>>>   }
> 

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[zhenglifeng (A)]

Hi Viresh,

I'd be happy to be a part of the reviewers list!

Thanks,
Lifeng

On 3/5/2026 2:32 PM, Viresh Kumar wrote:
> Added few more people
> 
> I think we should updated MAINTAINERS with a list of reviewers or maintainers
> for the CPPC driver. Who all want to be part of the reviewers list ?
> 
> On 03-03-26, 20:03, zhangpengjie (A) wrote:
>> Just a gentle ping on this patch.
>> Thanks, Pengjie
>>
>> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
>>> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
>>> linear performance scaling. Performance levels below this threshold
>>> are typically inefficient and should not be used by default.
>>>
>>> Currently, the QoS minimum request is initialized to 0. This defaults
>>> the performance floor to the absolute "Lowest Performance" state
>>> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
>>> an inefficient range unnecessarily.
>>>
>>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
>>> ---
>>> Changes in v2:
>>>    - Renamed the patch subject to better reflect the logic change.
>>>    - Updated the commit log to clarify ACPI spec details.
>>> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
>>> ---
>>>   drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>>>   1 file changed, 16 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>>> index 7e8042efedd1..4a3031d9fcf4 100644
>>> --- a/drivers/cpufreq/cppc_cpufreq.c
>>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>>> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>>>   	return target_freq;
>>>   }
>>> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
>>> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>>>   {
>>> -	cpufreq_verify_within_cpu_limits(policy);
>>> +	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
>>> +		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>>> +					      cpufreq_cpu_get(policy_data->cpu);
>>> +		struct cppc_cpudata *cpu_data;
>>> +
>>> +		if (!policy)
>>> +			return -EINVAL;
>>> +
>>> +		cpu_data = policy->driver_data;
>>> +		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
>>> +			cpu_data->perf_caps.lowest_nonlinear_perf);
>>> +	}
>>> +
>>> +	cpufreq_verify_within_cpu_limits(policy_data);
>>> +
>>>   	return 0;
>>>   }
> 

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Sumit Gupta]

Hi Viresh,

Happy to help with the reviews. You can add me to the reviewers list.

Thank you,
Sumit Gupta


On 05/03/26 12:02, Viresh Kumar wrote:
> External email: Use caution opening links or attachments
>
>
> Added few more people
>
> I think we should updated MAINTAINERS with a list of reviewers or maintainers
> for the CPPC driver. Who all want to be part of the reviewers list ?
>
> On 03-03-26, 20:03, zhangpengjie (A) wrote:
>> Just a gentle ping on this patch.
>> Thanks, Pengjie
>>
>> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
>>> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
>>> linear performance scaling. Performance levels below this threshold
>>> are typically inefficient and should not be used by default.
>>>
>>> Currently, the QoS minimum request is initialized to 0. This defaults
>>> the performance floor to the absolute "Lowest Performance" state
>>> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
>>> an inefficient range unnecessarily.
>>>
>>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
>>> ---
>>> Changes in v2:
>>>     - Renamed the patch subject to better reflect the logic change.
>>>     - Updated the commit log to clarify ACPI spec details.
>>> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
>>> ---
>>>    drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>>>    1 file changed, 16 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>>> index 7e8042efedd1..4a3031d9fcf4 100644
>>> --- a/drivers/cpufreq/cppc_cpufreq.c
>>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>>> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>>>      return target_freq;
>>>    }
>>> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
>>> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>>>    {
>>> -   cpufreq_verify_within_cpu_limits(policy);
>>> +   if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
>>> +           struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>>> +                                         cpufreq_cpu_get(policy_data->cpu);
>>> +           struct cppc_cpudata *cpu_data;
>>> +
>>> +           if (!policy)
>>> +                   return -EINVAL;
>>> +
>>> +           cpu_data = policy->driver_data;
>>> +           policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
>>> +                   cpu_data->perf_caps.lowest_nonlinear_perf);
>>> +   }
>>> +
>>> +   cpufreq_verify_within_cpu_limits(policy_data);
>>> +
>>>      return 0;
>>>    }
> --
> viresh

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Pierre Gondois]

Hello Viresh,

There are already quite some people, but please add me aswell.

Regards,
Pierre

On 3/5/26 07:32, Viresh Kumar wrote:
> Added few more people
>
> I think we should updated MAINTAINERS with a list of reviewers or maintainers
> for the CPPC driver. Who all want to be part of the reviewers list ?
>
> On 03-03-26, 20:03, zhangpengjie (A) wrote:
>> Just a gentle ping on this patch.
>> Thanks, Pengjie
>>
>> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
>>> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
>>> linear performance scaling. Performance levels below this threshold
>>> are typically inefficient and should not be used by default.
>>>
>>> Currently, the QoS minimum request is initialized to 0. This defaults
>>> the performance floor to the absolute "Lowest Performance" state
>>> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
>>> an inefficient range unnecessarily.
>>>
>>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
>>> ---
>>> Changes in v2:
>>>     - Renamed the patch subject to better reflect the logic change.
>>>     - Updated the commit log to clarify ACPI spec details.
>>> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
>>> ---
>>>    drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>>>    1 file changed, 16 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>>> index 7e8042efedd1..4a3031d9fcf4 100644
>>> --- a/drivers/cpufreq/cppc_cpufreq.c
>>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>>> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>>>    	return target_freq;
>>>    }
>>> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
>>> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>>>    {
>>> -	cpufreq_verify_within_cpu_limits(policy);
>>> +	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
>>> +		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>>> +					      cpufreq_cpu_get(policy_data->cpu);
>>> +		struct cppc_cpudata *cpu_data;
>>> +
>>> +		if (!policy)
>>> +			return -EINVAL;
>>> +
>>> +		cpu_data = policy->driver_data;
>>> +		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
>>> +			cpu_data->perf_caps.lowest_nonlinear_perf);
>>> +	}
>>> +
>>> +	cpufreq_verify_within_cpu_limits(policy_data);
>>> +
>>>    	return 0;
>>>    }

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Rafael J. Wysocki]

On Fri, Mar 6, 2026 at 4:09 PM Pierre Gondois <pierre.gondois@arm.com> wrote:
>
> Hello Viresh,
>
> There are already quite some people, but please add me aswell.

OK, so is there a consensus about this particular change?

I guess I'll need to take this one if everyone is fine with it because
I have picked up some ACPI CPPC library change that was combined with
cpufre_cppc code.

> On 3/5/26 07:32, Viresh Kumar wrote:
> > Added few more people
> >
> > I think we should updated MAINTAINERS with a list of reviewers or maintainers
> > for the CPPC driver. Who all want to be part of the reviewers list ?
> >
> > On 03-03-26, 20:03, zhangpengjie (A) wrote:
> >> Just a gentle ping on this patch.
> >> Thanks, Pengjie
> >>
> >> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
> >>> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
> >>> linear performance scaling. Performance levels below this threshold
> >>> are typically inefficient and should not be used by default.
> >>>
> >>> Currently, the QoS minimum request is initialized to 0. This defaults
> >>> the performance floor to the absolute "Lowest Performance" state
> >>> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
> >>> an inefficient range unnecessarily.
> >>>
> >>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> >>> ---
> >>> Changes in v2:
> >>>     - Renamed the patch subject to better reflect the logic change.
> >>>     - Updated the commit log to clarify ACPI spec details.
> >>> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
> >>> ---
> >>>    drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
> >>>    1 file changed, 16 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> >>> index 7e8042efedd1..4a3031d9fcf4 100644
> >>> --- a/drivers/cpufreq/cppc_cpufreq.c
> >>> +++ b/drivers/cpufreq/cppc_cpufreq.c
> >>> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
> >>>     return target_freq;
> >>>    }
> >>> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
> >>> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
> >>>    {
> >>> -   cpufreq_verify_within_cpu_limits(policy);
> >>> +   if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
> >>> +           struct cpufreq_policy *policy __free(put_cpufreq_policy) =
> >>> +                                         cpufreq_cpu_get(policy_data->cpu);
> >>> +           struct cppc_cpudata *cpu_data;
> >>> +
> >>> +           if (!policy)
> >>> +                   return -EINVAL;
> >>> +
> >>> +           cpu_data = policy->driver_data;
> >>> +           policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
> >>> +                   cpu_data->perf_caps.lowest_nonlinear_perf);
> >>> +   }
> >>> +
> >>> +   cpufreq_verify_within_cpu_limits(policy_data);
> >>> +
> >>>     return 0;
> >>>    }

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[zhenglifeng (A)]

Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>

On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
> linear performance scaling. Performance levels below this threshold
> are typically inefficient and should not be used by default.
> 
> Currently, the QoS minimum request is initialized to 0. This defaults
> the performance floor to the absolute "Lowest Performance" state
> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
> an inefficient range unnecessarily.
> 
> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> ---
> Changes in v2:
>   - Renamed the patch subject to better reflect the logic change.
>   - Updated the commit log to clarify ACPI spec details.
> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
> ---
>  drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 7e8042efedd1..4a3031d9fcf4 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>  	return target_freq;
>  }
>  
> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>  {
> -	cpufreq_verify_within_cpu_limits(policy);
> +	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
> +		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
> +					      cpufreq_cpu_get(policy_data->cpu);
> +		struct cppc_cpudata *cpu_data;
> +
> +		if (!policy)
> +			return -EINVAL;
> +
> +		cpu_data = policy->driver_data;
> +		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
> +			cpu_data->perf_caps.lowest_nonlinear_perf);
> +	}
> +
> +	cpufreq_verify_within_cpu_limits(policy_data);
> +
>  	return 0;
>  }
>  

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Jie Zhan]

On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
> linear performance scaling. Performance levels below this threshold
> are typically inefficient and should not be used by default.
> 
> Currently, the QoS minimum request is initialized to 0. This defaults
I'm more curious on the original commit that overrides the policy->min set
by driver, which is:
521223d8b3ec ("cpufreq: Fix initialization of min and max frequency QoS requests")

The changelog says:
"The min and max frequency QoS requests in the cpufreq core are initialized
to whatever the current min and max frequency values are at the init time,
but if any of these values change later (for example, cpuinfo.max_freq is
updated by the driver), these initial request values will be limiting the
CPU frequency unnecessarily unless they are changed by user space via
sysfs."

So, instead of doing what the patch did, what about calling
freq_qos_update_request(policy->max_freq_req, xxx) when cpuinfo.max_freq is
updated?

Jie

> the performance floor to the absolute "Lowest Performance" state
> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
> an inefficient range unnecessarily.
> 
> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
> ---
> Changes in v2:
>   - Renamed the patch subject to better reflect the logic change.
>   - Updated the commit log to clarify ACPI spec details.
> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
> ---
>  drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 7e8042efedd1..4a3031d9fcf4 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>  	return target_freq;
>  }
>  
> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>  {
> -	cpufreq_verify_within_cpu_limits(policy);
> +	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
> +		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
> +					      cpufreq_cpu_get(policy_data->cpu);
> +		struct cppc_cpudata *cpu_data;
> +
> +		if (!policy)
> +			return -EINVAL;
> +
> +		cpu_data = policy->driver_data;
> +		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
> +			cpu_data->perf_caps.lowest_nonlinear_perf);
> +	}
> +
> +	cpufreq_verify_within_cpu_limits(policy_data);
> +
>  	return 0;
>  }
>  

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[zhangpengjie (A)]

Hi Jie,

On 3/5/2026 9:49 PM, Jie Zhan wrote:
>
> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
>> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
>> linear performance scaling. Performance levels below this threshold
>> are typically inefficient and should not be used by default.
>>
>> Currently, the QoS minimum request is initialized to 0. This defaults
> I'm more curious on the original commit that overrides the policy->min set
> by driver, which is:
> 521223d8b3ec ("cpufreq: Fix initialization of min and max frequency QoS requests")
>
> The changelog says:
> "The min and max frequency QoS requests in the cpufreq core are initialized
> to whatever the current min and max frequency values are at the init time,
> but if any of these values change later (for example, cpuinfo.max_freq is
> updated by the driver), these initial request values will be limiting the
> CPU frequency unnecessarily unless they are changed by user space via
> sysfs."
>
> So, instead of doing what the patch did, what about calling
> freq_qos_update_request(policy->max_freq_req, xxx) when cpuinfo.max_freq is
> updated?
>
> Jie

Thanks for pointing this out.

I think commit 521223d8b3ec intentionally changed the semantics of the
core min/max QoS requests so that they no longer reflect the initial
policy limits set by the driver. Instead, they stay at the default
"no constraint" values until user space (or another QoS client) updates
them. That makes sense for the problem described in that changelog.

What my patch is trying to address is a slightly different issue in
cppc_cpufreq: the driver currently treats `lowest_nonlinear_perf` as
the default minimum policy floor, but with the current core semantics
that floor is not represented explicitly and gets lost during policy
initialization.

So I agree that calling freq_qos_update_request() when
cpuinfo.min_freq/max_freq changes is the right approach for stale
request updates, but I am not sure it addresses the question
for `lowest_nonlinear_perf` itself:

Should it be modeled as a hard driver constraint, or only as the
default minimum policy value that user space may still lower explicitly?

My patch assumes the latter, although I agree the current implementation
is not the cleanest way to express it.

Thanks,
         Pengjie


>> the performance floor to the absolute "Lowest Performance" state
>> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
>> an inefficient range unnecessarily.
>>
>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
>> ---
>> Changes in v2:
>>    - Renamed the patch subject to better reflect the logic change.
>>    - Updated the commit log to clarify ACPI spec details.
>> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
>> ---
>>   drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>>   1 file changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>> index 7e8042efedd1..4a3031d9fcf4 100644
>> --- a/drivers/cpufreq/cppc_cpufreq.c
>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>>   	return target_freq;
>>   }
>>   
>> -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
>> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>>   {
>> -	cpufreq_verify_within_cpu_limits(policy);
>> +	if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
>> +		struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>> +					      cpufreq_cpu_get(policy_data->cpu);
>> +		struct cppc_cpudata *cpu_data;
>> +
>> +		if (!policy)
>> +			return -EINVAL;
>> +
>> +		cpu_data = policy->driver_data;
>> +		policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
>> +			cpu_data->perf_caps.lowest_nonlinear_perf);
>> +	}
>> +
>> +	cpufreq_verify_within_cpu_limits(policy_data);
>> +
>>   	return 0;
>>   }
>>   

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Jie Zhan]

On 3/9/2026 9:16 PM, zhangpengjie (A) wrote:
> Hi Jie,
> 
> On 3/5/2026 9:49 PM, Jie Zhan wrote:
>>
>> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
>>> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
>>> linear performance scaling. Performance levels below this threshold
>>> are typically inefficient and should not be used by default.
>>>
>>> Currently, the QoS minimum request is initialized to 0. This defaults
>> I'm more curious on the original commit that overrides the policy->min set
>> by driver, which is:
>> 521223d8b3ec ("cpufreq: Fix initialization of min and max frequency QoS requests")
>>
>> The changelog says:
>> "The min and max frequency QoS requests in the cpufreq core are initialized
>> to whatever the current min and max frequency values are at the init time,
>> but if any of these values change later (for example, cpuinfo.max_freq is
>> updated by the driver), these initial request values will be limiting the
>> CPU frequency unnecessarily unless they are changed by user space via
>> sysfs."
>>
>> So, instead of doing what the patch did, what about calling
>> freq_qos_update_request(policy->max_freq_req, xxx) when cpuinfo.max_freq is
>> updated?
>>
>> Jie
> 
> Thanks for pointing this out.
> 
> I think commit 521223d8b3ec intentionally changed the semantics of the
> core min/max QoS requests so that they no longer reflect the initial
> policy limits set by the driver. Instead, they stay at the default
> "no constraint" values until user space (or another QoS client) updates
> them. That makes sense for the problem described in that changelog.
> 
> What my patch is trying to address is a slightly different issue in
> cppc_cpufreq: the driver currently treats `lowest_nonlinear_perf` as
> the default minimum policy floor, but with the current core semantics
> that floor is not represented explicitly and gets lost during policy
> initialization.
Yeah, the current status:
Setting 'policy->min' in driver->init() is pointless at the moment, while
some drivers are still doing it.  The effective place to set 'policy->min'
became driver->verify(), but a minor side effect by doing so is
'policy->min' can't be preserved on switching governors.
> 
> So I agree that calling freq_qos_update_request() when
> cpuinfo.min_freq/max_freq changes is the right approach for stale
> request updates, but I am not sure it addresses the question
> for `lowest_nonlinear_perf` itself:
I was talking about calling freq_qos_update_request() in commit
521223d8b3ec.
> 
> Should it be modeled as a hard driver constraint, or only as the
> default minimum policy value that user space may still lower explicitly?
> 
> My patch assumes the latter, although I agree the current implementation
> is not the cleanest way to express it.
> 
> Thanks,
>         Pengjie
> 
> 
Does [1] also solve this issue by chance? especially Patch 5.
If so, I think we may follow that up and get the framework to a sensible
shape.
[1] https://lore.kernel.org/linux-pm/20260225084930.1692228-1-pierre.gondois@arm.com/
>>> the performance floor to the absolute "Lowest Performance" state
>>> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
>>> an inefficient range unnecessarily.
>>>
>>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
>>> ---
>>> Changes in v2:
>>>    - Renamed the patch subject to better reflect the logic change.
>>>    - Updated the commit log to clarify ACPI spec details.
>>> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
>>> ---
>>>   drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>>>   1 file changed, 16 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>>> index 7e8042efedd1..4a3031d9fcf4 100644
>>> --- a/drivers/cpufreq/cppc_cpufreq.c
>>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>>> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>>>       return target_freq;
>>>   }
>>>   -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
>>> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>>>   {
>>> -    cpufreq_verify_within_cpu_limits(policy);
>>> +    if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
>>> +        struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>>> +                          cpufreq_cpu_get(policy_data->cpu);
>>> +        struct cppc_cpudata *cpu_data;
>>> +
>>> +        if (!policy)
>>> +            return -EINVAL;
>>> +
>>> +        cpu_data = policy->driver_data;
>>> +        policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
>>> +            cpu_data->perf_caps.lowest_nonlinear_perf);
>>> +    }
>>> +
>>> +    cpufreq_verify_within_cpu_limits(policy_data);
>>> +
>>>       return 0;
>>>   }
>>>   

Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Pierre Gondois]

On 3/10/26 10:12, Jie Zhan wrote:
>
> On 3/9/2026 9:16 PM, zhangpengjie (A) wrote:
>> Hi Jie,
>>
>> On 3/5/2026 9:49 PM, Jie Zhan wrote:
>>> On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
>>>> The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
>>>> linear performance scaling. Performance levels below this threshold
>>>> are typically inefficient and should not be used by default.
>>>>
>>>> Currently, the QoS minimum request is initialized to 0. This defaults
>>> I'm more curious on the original commit that overrides the policy->min set
>>> by driver, which is:
>>> 521223d8b3ec ("cpufreq: Fix initialization of min and max frequency QoS requests")
>>>
>>> The changelog says:
>>> "The min and max frequency QoS requests in the cpufreq core are initialized
>>> to whatever the current min and max frequency values are at the init time,
>>> but if any of these values change later (for example, cpuinfo.max_freq is
>>> updated by the driver), these initial request values will be limiting the
>>> CPU frequency unnecessarily unless they are changed by user space via
>>> sysfs."
>>>
>>> So, instead of doing what the patch did, what about calling
>>> freq_qos_update_request(policy->max_freq_req, xxx) when cpuinfo.max_freq is
>>> updated?
>>>
>>> Jie
>> Thanks for pointing this out.
>>
>> I think commit 521223d8b3ec intentionally changed the semantics of the
>> core min/max QoS requests so that they no longer reflect the initial
>> policy limits set by the driver. Instead, they stay at the default
>> "no constraint" values until user space (or another QoS client) updates
>> them. That makes sense for the problem described in that changelog.
>>
>> What my patch is trying to address is a slightly different issue in
>> cppc_cpufreq: the driver currently treats `lowest_nonlinear_perf` as
>> the default minimum policy floor, but with the current core semantics
>> that floor is not represented explicitly and gets lost during policy
>> initialization.
> Yeah, the current status:
> Setting 'policy->min' in driver->init() is pointless at the moment, while
> some drivers are still doing it.  The effective place to set 'policy->min'
> became driver->verify(), but a minor side effect by doing so is
> 'policy->min' can't be preserved on switching governors.
>> So I agree that calling freq_qos_update_request() when
>> cpuinfo.min_freq/max_freq changes is the right approach for stale
>> request updates, but I am not sure it addresses the question
>> for `lowest_nonlinear_perf` itself:
> I was talking about calling freq_qos_update_request() in commit
> 521223d8b3ec.
>> Should it be modeled as a hard driver constraint, or only as the
>> default minimum policy value that user space may still lower explicitly?
>>
>> My patch assumes the latter, although I agree the current implementation
>> is not the cleanest way to express it.
>>
>> Thanks,
>>          Pengjie
>>
>>
> Does [1] also solve this issue by chance? especially Patch 5.
> If so, I think we may follow that up and get the framework to a sensible
> shape.
> [1] https://lore.kernel.org/linux-pm/20260225084930.1692228-1-pierre.gondois@arm.com/

Yes right, this should help:

+ /* + * If the driver has set policy->min or max, + * use the value as 
a QoS request. + */ + min = max(FREQ_QOS_MIN_DEFAULT_VALUE, 
policy->min); + if (policy->max) + max = min(FREQ_QOS_MAX_DEFAULT_VALUE, 
policy->max); + else + max = FREQ_QOS_MAX_DEFAULT_VALUE;

However in the patchset, policy->min is not set to the lowest non linear 
freq.,
so this would have to be done aswell.

------

It also seem preferable to set the min QOS value once at init rather that
re-computing it on each ->verify() call.


>>>> the performance floor to the absolute "Lowest Performance" state
>>>> instead of "lowest_nonlinear_perf", allowing the CPU to operate in
>>>> an inefficient range unnecessarily.
>>>>
>>>> Signed-off-by: Pengjie Zhang <zhangpengjie2@huawei.com>
>>>> ---
>>>> Changes in v2:
>>>>     - Renamed the patch subject to better reflect the logic change.
>>>>     - Updated the commit log to clarify ACPI spec details.
>>>> Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@huawei.com/
>>>> ---
>>>>    drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
>>>>    1 file changed, 16 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>>>> index 7e8042efedd1..4a3031d9fcf4 100644
>>>> --- a/drivers/cpufreq/cppc_cpufreq.c
>>>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>>>> @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
>>>>        return target_freq;
>>>>    }
>>>>    -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
>>>> +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
>>>>    {
>>>> -    cpufreq_verify_within_cpu_limits(policy);
>>>> +    if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
>>>> +        struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>>>> +                          cpufreq_cpu_get(policy_data->cpu);
>>>> +        struct cppc_cpudata *cpu_data;
>>>> +
>>>> +        if (!policy)
>>>> +            return -EINVAL;
>>>> +
>>>> +        cpu_data = policy->driver_data;
>>>> +        policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
>>>> +            cpu_data->perf_caps.lowest_nonlinear_perf);
>>>> +    }
>>>> +
>>>> +    cpufreq_verify_within_cpu_limits(policy_data);
>>>> +
>>>>        return 0;
>>>>    }
>>>>