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@xxxxxxxxxx>
>>> ---
>>> 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@xxxxxxxxxx/
>>> ---
>>>   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;
>>>   }
>