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

["zhenglifeng (A)" <zhenglifeng1@huawei.com>]

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/

> -		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.

>  	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;