Re: [PATCH v1] cpufreq: Make cpufreq_update_pressure() fall back to cpuinfo.max_freq

[Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>]

On 7/8/2026 11:44 AM, Viresh Kumar wrote:
> On 07-07-26, 19:25, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>
>> If arch_scale_freq_ref() is not defined for a given arch (like x86, for
>> example), cpufreq_update_pressure() will always set cpufreq_pressure to
>> zero for all CPUs in the system, which is generally problematic on
>> systems with asymmetric capacity [1].
>>
>> However, in the absence of arch_scale_freq_ref(), it is reasonable
>> to assume that cpuinfo.max_freq is the maximum sustainable frequency
>> for the given cpufreq policy.  Moreover, there are cases in which
>> arch_scale_freq_ref() would need to be defined to return essentially
>> the cpuinfo.max_freq value anyway (for example, intel_pstate on
>> hybrid platforms).
>>
>> For the above reasons, update cpufreq_update_pressure() to fall back to
>> using cpuinfo.max_freq as the reference frequency if zero is returned by
>> arch_scale_freq_ref().
>>
>> Fixes: 75d659317bb1 ("cpufreq: Add a cpufreq pressure feedback for the scheduler")
>> Link: https://lore.kernel.org/lkml/CAKfTPtBuRLfYNnR4w--cFZYZy-R8gaPEgVwCcaMmbCcJ2H-muQ@mail.gmail.com/ [1]
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> ---
>>   drivers/cpufreq/cpufreq.c |    3 +++
>>   1 file changed, 3 insertions(+)
>>
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -2590,6 +2590,9 @@ static void cpufreq_update_pressure(stru
>>   
>>   	cpu = cpumask_first(policy->related_cpus);
>>   	max_freq = arch_scale_freq_ref(cpu);
>> +	if (!max_freq)
>> +		max_freq = policy->cpuinfo.max_freq;
>> +
>>   	capped_freq = policy->max;
>>   
>>   	/*
> 
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> 

Reviewed-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>

-- 
Thx and BRs,
Zhongqiu Han