Re: [PATCH 2/6] cpufreq: Add boost_freq_req QoS request

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

Hello Lifeng,

Thanks for the review,

On 1/31/26 05:00, zhenglifeng (A) wrote:
> On 2026/1/26 18:18, Pierre Gondois wrote:
>> The Power Management Quality of Service (PM QoS) allows to
>> aggregate constraints from multiple entities. It is currently
>> used to manage the min/max frequency of a given policy.
>>
>> Frequency constraints can come for instance from:
>> - Thermal framework: acpi_thermal_cpufreq_init()
>> - Firmware: _PPC objects: acpi_processor_ppc_init()
>> - User: by setting policyX/scaling_[min|max]_freq
>> The minimum of the max frequency constraints is used to compute
>> the resulting maximum allowed frequency.
>>
>> When enabling boost frequencies, the same frequency request object
>> (policy->max_freq_req) as to handle requests from users is used.
>> As a result, when setting:
>> - scaling_max_freq
>> - boost
>> The last sysfs file used overwrites the request from the other
>> sysfs file.
>>
>> To avoid this, create a per-policy boost_freq_req to save the boost
>> constraints instead of overwriting the last scaling_max_freq
>> constraint.
>>
>> Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
>> ---
>>   drivers/cpufreq/cpufreq.c | 40 ++++++++++++++++++++++++++++++++++-----
>>   include/linux/cpufreq.h   |  1 +
>>   2 files changed, 36 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index db414c052658b..c8fb4c6656e94 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1359,17 +1359,24 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
>>   	/* Cancel any pending policy->update work before freeing the policy. */
>>   	cancel_work_sync(&policy->update);
>>   
>> -	if (policy->max_freq_req) {
>> +	if (policy->max_freq_req || policy->boost_freq_req) {
>>   		/*
>> -		 * Remove max_freq_req after sending CPUFREQ_REMOVE_POLICY
>> -		 * notification, since CPUFREQ_CREATE_POLICY notification was
>> -		 * sent after adding max_freq_req earlier.
>> +		 * Remove max/boost _freq_req after sending CPUFREQ_REMOVE_POLICY
>> +		 * notification, since CPUFREQ_CREATE_POLICY notification was sent
>> +		 * after adding max/boost _freq_req earlier.
>>   		 */
>>   		blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
>>   					     CPUFREQ_REMOVE_POLICY, policy);
> As we discussed in [1], CPUFREQ_REMOVE_POLICY notification will be sent
> here without sending CPUFREQ_CREATE_POLICY notification before if adding
> boost_freq_req fails.
>
> [1] https://lore.kernel.org/all/a615ab13-bd54-4051-ae61-2bfe8b59427e@arm.com/

Yes right indeed.
The following condition should be more correct:

if ((policy->max_freq_req && !policy->boost_supported) || 
policy->boost_freq_req) {

  ...

}

>> -		freq_qos_remove_request(policy->max_freq_req);
>>   	}
>>   
>> +	if (policy->boost_freq_req) {
>> +		freq_qos_remove_request(policy->boost_freq_req);
>> +		kfree(policy->boost_freq_req);
>> +	}
>> +
>> +	if (policy->max_freq_req)
>> +		freq_qos_remove_request(policy->max_freq_req);
>> +
> Thses two 'if's are unnecessary. It's OK to call freq_qos_remove_request
> and kfree when the QoS request is NULL.

Ok


>>   	freq_qos_remove_request(policy->min_freq_req);
>>   	kfree(policy->min_freq_req);
>>   
>> @@ -1479,6 +1486,29 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
>>   			goto out_destroy_policy;
>>   		}
>>   
>> +		if (policy->boost_supported) {
>> +			policy->boost_freq_req = kzalloc(sizeof(*policy->boost_freq_req),
>> +							 GFP_KERNEL);
>> +			if (!policy->boost_freq_req) {
>> +				ret = -ENOMEM;
>> +				goto out_destroy_policy;
>> +			}
>> +
>> +			ret = freq_qos_add_request(&policy->constraints,
>> +						   policy->boost_freq_req,
>> +						   FREQ_QOS_MAX,
>> +						   FREQ_QOS_MAX_DEFAULT_VALUE);
>> +			if (ret < 0) {
>> +				/*
>> +				 * So we don't call freq_qos_remove_request() for an
>> +				 * uninitialized request.
>> +				 */
>> +				kfree(policy->boost_freq_req);
>> +				policy->boost_freq_req = NULL;
>> +				goto out_destroy_policy;
>> +			}
>> +		}
>> +
>>   		blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
>>   				CPUFREQ_CREATE_POLICY, policy);
>>   	}
>> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
>> index 0465d1e6f72ac..c292a6a19e4f5 100644
>> --- a/include/linux/cpufreq.h
>> +++ b/include/linux/cpufreq.h
>> @@ -81,6 +81,7 @@ struct cpufreq_policy {
>>   	struct freq_constraints	constraints;
>>   	struct freq_qos_request	*min_freq_req;
>>   	struct freq_qos_request	*max_freq_req;
>> +	struct freq_qos_request *boost_freq_req;
>>   
>>   	struct cpufreq_frequency_table	*freq_table;
>>   	enum cpufreq_table_sorting freq_table_sorted;