Re: [PATCH v2 4/4] cpufreq: Use policy->min/max init as QoS request

[Pierre Gondois <pierre.gondois@arm.com>]

Hello Lifeng,

On 5/21/26 13:26, zhenglifeng (A) wrote:
> On 5/11/2026 9:55 PM, Pierre Gondois wrote:
>> Consider policy->min/max being set in the driver .init()
>> callback as a QoS request. Impacted driver are:
>> - gx-suspmod.c (min)
>> - cppc-cpufreq.c (min)
>> - longrun.c (min/max)
>>
>> Update the documentation accordingly.
>>
>> Signed-off-by: Pierre Gondois<pierre.gondois@arm.com>
>> ---
>>   Documentation/cpu-freq/cpu-drivers.rst | 10 ++++++++--
>>   drivers/cpufreq/cpufreq.c              | 12 ++++++++++--
>>   2 files changed, 18 insertions(+), 4 deletions(-)
>>
>> diff --git a/Documentation/cpu-freq/cpu-drivers.rst b/Documentation/cpu-freq/cpu-drivers.rst
>> index c5635ac3de547..ab4f3c0f3a89b 100644
>> --- a/Documentation/cpu-freq/cpu-drivers.rst
>> +++ b/Documentation/cpu-freq/cpu-drivers.rst
>> @@ -114,8 +114,14 @@ Then, the driver must fill in the following values:
>>   |policy->cur			    | The current operating frequency of   |
>>   |				    | this CPU (if appropriate)		   |
>>   +-----------------------------------+--------------------------------------+
>> -|policy->min,			    |					   |
>> -|policy->max,			    |					   |
>> +|policy->min			    | If set by the driver in ->init(),    |
>> +|				    | used as initial minimum frequency	   |
>> +|				    | QoS request.			   |
>> ++-----------------------------------+--------------------------------------+
>> +|policy->max			    | If set by the driver in ->init(),    |
>> +|				    | used as initial maximum frequency	   |
>> +|				    | QoS request.			   |
>> ++-----------------------------------+--------------------------------------+
>>   |policy->policy and, if necessary,  |					   |
>>   |policy->governor		    | must contain the "default policy" for|
>>   |				    | this CPU. A few moments later,       |
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 9e2d9d3fc5351..9a005367ed87b 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1399,8 +1399,16 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
>>   
>>   static int cpufreq_policy_init_qos(struct cpufreq_policy *policy)
>>   {
>> +	unsigned int min_freq, max_freq;
>>   	int ret;
>>   
>> +	/* Use policy->min/max set by the driver as QoS requests. */
>> +	min_freq = max(FREQ_QOS_MIN_DEFAULT_VALUE, policy->min);
>> +	if (policy->max)
>> +		max_freq = min(FREQ_QOS_MAX_DEFAULT_VALUE, policy->max);
>> +	else
>> +		max_freq = FREQ_QOS_MAX_DEFAULT_VALUE;
>> +
> Can't see the point of this. Why not just use policy->max and policy->min
> to init qos?

With patch [3/4] "cpufreq: Remove driver default policy->min/max init",

some drivers don't set policy->min/max. For the max value, we would end-up

with a max QoS constraint of 0.

If we were to use cpuinfo.max_freq instead, then we this would bring us

back to:

521223d8b3ec ("cpufreq: Fix initialization of min and max
frequency QoS requests")


>>   	/*
>>   	 * If the driver didn't set policy->min/max, set them as
>>   	 * they are used to clamp frequency requests.
>> @@ -1418,12 +1426,12 @@ static int cpufreq_policy_init_qos(struct cpufreq_policy *policy)
>>   	}
>>   
>>   	ret = freq_qos_add_request(&policy->constraints, &policy->min_freq_req,
>> -				   FREQ_QOS_MIN, FREQ_QOS_MIN_DEFAULT_VALUE);
>> +				   FREQ_QOS_MIN, min_freq);
>>   	if (ret < 0)
>>   		return ret;
>>   
>>   	ret = freq_qos_add_request(&policy->constraints, &policy->max_freq_req,
>> -				   FREQ_QOS_MAX, FREQ_QOS_MAX_DEFAULT_VALUE);
>> +				   FREQ_QOS_MAX, max_freq);
>>   	if (ret < 0)
>>   		return ret;
>>