linux-kernel - Re: [PATCH v1 2/4] cpufreq: Add boost_freq

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Message-ID: <41ad3fe6-59e3-43b7-b346-3ba3cc460826@arm.com>
Date: Mon, 8 Dec 2025 11:25:05 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: "zhenglifeng (A)" <zhenglifeng1@...wei.com>
Cc: linux-kernel@...r.kernel.org, Christian Loehle
 <christian.loehle@....com>, Ionela Voinescu <ionela.voinescu@....com>,
 Jie Zhan <zhanjie9@...ilicon.com>, Huang Rui <ray.huang@....com>,
 "Gautham R. Shenoy" <gautham.shenoy@....com>,
 Mario Limonciello <mario.limonciello@....com>,
 Perry Yuan <perry.yuan@....com>, "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org
Subject: Re: [PATCH v1 2/4] cpufreq: Add boost_freq_req QoS request


On 12/4/25 12:50, zhenglifeng (A) wrote:
> On 2025/12/4 18:13, 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@....com>
>> ---
>>   drivers/cpufreq/cpufreq.c | 35 +++++++++++++++++++++++++++++++++++
>>   include/linux/cpufreq.h   |  1 +
>>   2 files changed, 36 insertions(+)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 11b29c7dbea9e..23f64346b80f8 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1370,6 +1370,18 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
>>   		freq_qos_remove_request(policy->max_freq_req);
>>   	}
>>   
>> +	if (policy->boost_freq_req) {
>> +		/*
>> +		 * Remove boost_freq_req after sending CPUFREQ_REMOVE_POLICY
>> +		 * notification, since CPUFREQ_CREATE_POLICY notification was
>> +		 * sent after adding boost_freq_req earlier.
>> +		 */
>> +		blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
>> +					     CPUFREQ_REMOVE_POLICY, policy);
> The CPUFREQ_REMOVE_POLICY notification is sent before removing
> max_freq_req, I don't think it should be sent again here.
Yes indeed
>> +		freq_qos_remove_request(policy->boost_freq_req);
>> +		kfree(policy->boost_freq_req);
>> +	}
>> +
> I think boost_freq_req should be removed before removing max_freq_req,
> since it was added after adding max_freq_req as shown below.

Ok right

>>   	freq_qos_remove_request(policy->min_freq_req);
>>   	kfree(policy->min_freq_req);
>>   
>> @@ -1476,6 +1488,29 @@ 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;