[PATCH v2] cpufreq: queue policy->update work to a dedicated thread

[Gaowei Pu <pugaowei@oppo.com>]

We should ensure the low schedule latency of cpu frequency limits work
to meet performance and power demands. so queue the policy->update work
to a dedicated thread.

Remove the rt setting of the thread in patch v1 at Tim and
Rafael J's request. However, it's will not meet everyone's request
when we add a dedicated highpri workqueue to do the policy update work.
Therefore, we keep the thread and will add a vendor hook in andorid aosp
branch lately so we can customize the thread conveniently.

Changes in v2:
- Remove the rt setting of the thread and rephrase commit msg.
- Link to v1: https://lore.kernel.org/lkml/20240717063321.629-1-pugaowei@oppo.com/

Signed-off-by: Gaowei Pu <pugaowei@oppo.com>
---
 drivers/cpufreq/cpufreq.c | 23 +++++++++++++++++------
 include/linux/cpufreq.h   |  4 +++-
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index d7426e1d8bdd..3980f6789a17 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1196,7 +1196,7 @@ void refresh_frequency_limits(struct cpufreq_policy *policy)
 }
 EXPORT_SYMBOL(refresh_frequency_limits);
 
-static void handle_update(struct work_struct *work)
+static void handle_update(struct kthread_work *work)
 {
 	struct cpufreq_policy *policy =
 		container_of(work, struct cpufreq_policy, update);
@@ -1213,7 +1213,7 @@ static int cpufreq_notifier_min(struct notifier_block *nb, unsigned long freq,
 {
 	struct cpufreq_policy *policy = container_of(nb, struct cpufreq_policy, nb_min);
 
-	schedule_work(&policy->update);
+	kthread_queue_work(policy->worker, &policy->update);
 	return 0;
 }
 
@@ -1222,7 +1222,7 @@ static int cpufreq_notifier_max(struct notifier_block *nb, unsigned long freq,
 {
 	struct cpufreq_policy *policy = container_of(nb, struct cpufreq_policy, nb_max);
 
-	schedule_work(&policy->update);
+	kthread_queue_work(policy->worker, &policy->update);
 	return 0;
 }
 
@@ -1305,14 +1305,23 @@ static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
 		goto err_min_qos_notifier;
 	}
 
+	policy->worker = kthread_create_worker_on_cpu(cpu, 0, "policy_worker%d", cpu);
+	if (IS_ERR(policy->worker)) {
+		dev_err(dev, "Failed to create policy_worker%d\n", cpu);
+		goto err_max_qos_notifier;
+	}
+
 	INIT_LIST_HEAD(&policy->policy_list);
 	init_rwsem(&policy->rwsem);
 	spin_lock_init(&policy->transition_lock);
 	init_waitqueue_head(&policy->transition_wait);
-	INIT_WORK(&policy->update, handle_update);
+	kthread_init_work(&policy->update, handle_update);
 
 	return policy;
 
+err_max_qos_notifier:
+	freq_qos_remove_notifier(&policy->constraints, FREQ_QOS_MAX,
+				 &policy->nb_max);
 err_min_qos_notifier:
 	freq_qos_remove_notifier(&policy->constraints, FREQ_QOS_MIN,
 				 &policy->nb_min);
@@ -1356,7 +1365,9 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
 				 &policy->nb_min);
 
 	/* Cancel any pending policy->update work before freeing the policy. */
-	cancel_work_sync(&policy->update);
+	kthread_cancel_work_sync(&policy->update);
+	if (policy->worker)
+		kthread_destroy_worker(policy->worker);
 
 	if (policy->max_freq_req) {
 		/*
@@ -1827,7 +1838,7 @@ static unsigned int cpufreq_verify_current_freq(struct cpufreq_policy *policy, b
 
 		cpufreq_out_of_sync(policy, new_freq);
 		if (update)
-			schedule_work(&policy->update);
+			kthread_queue_work(policy->worker, &policy->update);
 	}
 
 	return new_freq;
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 95f3807c8c55..728fa00a9647 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -20,6 +20,7 @@
 #include <linux/spinlock.h>
 #include <linux/sysfs.h>
 #include <linux/minmax.h>
+#include <linux/kthread.h>
 
 /*********************************************************************
  *                        CPUFREQ INTERFACE                          *
@@ -77,8 +78,9 @@ struct cpufreq_policy {
 	void			*governor_data;
 	char			last_governor[CPUFREQ_NAME_LEN]; /* last governor used */
 
-	struct work_struct	update; /* if update_policy() needs to be
+	struct kthread_work	update; /* if update_policy() needs to be
 					 * called, but you're in IRQ context */
+	struct kthread_worker *worker;
 
 	struct freq_constraints	constraints;
 	struct freq_qos_request	*min_freq_req;
-- 
2.17.1