Re: [PATCH v2 1/3] cpufreq: Add boost_freq_req QoS request

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

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@arm.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:

@@ -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;