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Message-ID: <a615ab13-bd54-4051-ae61-2bfe8b59427e@arm.com>
Date: Wed, 17 Dec 2025 17:21:54 +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 v2 1/3] cpufreq: Add boost_freq_req QoS request
On 12/10/25 04:01, zhenglifeng (A) wrote:
> On 2025/12/8 18:59, 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 | 28 ++++++++++++++++++++++++++++
>> include/linux/cpufreq.h | 1 +
>> 2 files changed, 29 insertions(+)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 852e024facc3c..942416f2741b0 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1359,6 +1359,11 @@ 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->boost_freq_req) {
>> + freq_qos_remove_request(policy->boost_freq_req);
>> + kfree(policy->boost_freq_req);
>> + }
>> +
>> if (policy->max_freq_req) {
>> /*
>> * Remove max_freq_req after sending CPUFREQ_REMOVE_POLICY
> If adding boost_freq_req fails, CPUFREQ_CREATE_POLICY notification will
> never be sent but CPUFREQ_REMOVE_POLICY notification will be sent here. So
> maybe something like this is better:
Yes right indeed.
However cf. what you suggested in patch 3/3 I believe, it might be necessary
to always set boost_freq_req, even for drivers that don't actually
support boost
frequencies.
This might simplify this patch.
>
> @@ -1365,17 +1365,28 @@ 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->boost_freq_req) {
> /*
> - * Remove max_freq_req after sending CPUFREQ_REMOVE_POLICY
> + * Remove boost_freq_req after sending CPUFREQ_REMOVE_POLICY
> * notification, since CPUFREQ_CREATE_POLICY notification was
> - * sent after adding max_freq_req earlier.
> + * sent after adding boost_freq_req earlier.
> */
> blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
> CPUFREQ_REMOVE_POLICY, policy);
> - freq_qos_remove_request(policy->max_freq_req);
> + freq_qos_remove_request(policy->boost_freq_req);
> + kfree(policy->boost_freq_req);
> }
>
> + if (policy->max_freq_req && !policy->boost_supported) {
> + /*
> + * Send CPUFREQ_REMOVE_POLICY notification here if
> + * boost_freq_req is not present.
> + */
> + blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
> + CPUFREQ_REMOVE_POLICY, policy);
> + }
> +
> + freq_qos_remove_request(policy->max_freq_req);
> freq_qos_remove_request(policy->min_freq_req);
> kfree(policy->min_freq_req);
>
> ---
> It's a bit verbose, but I can't think of a better way.
>
>> @@ -1476,6 +1481,29 @@ 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);
>> } else {
>> 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;
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