[PATCH RFC 1/2] thermal/cpu idle cooling: Introduce cpu idle cooling driver

[Tao Wang]

cpu idle cooling driver performs synchronized idle injection across
all cpu in same cluster, offers a new method to cooling down cpu,
that is similar to intel_power_clamp driver, but is basically
designed for ARM platform.
Each cluster has its own idle cooling device, each core has its own
idle injection thread, idle injection thread use play_idle to enter
idle. In order to reach deepest idle state, all cores are aligned by
jiffies. the injected idle ratio can be controlled through cooling
device interface.

Signed-off-by: Tao Wang <kevin.wangtao@xxxxxxxxxxxxx>
---
 drivers/thermal/Kconfig            |   13 +
 drivers/thermal/Makefile           |    3 +
 drivers/thermal/cpu_idle_cooling.c |  648 ++++++++++++++++++++++++++++++++++++
 3 files changed, 664 insertions(+)
 create mode 100644 drivers/thermal/cpu_idle_cooling.c

diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index b5b5fac..f78e85c 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -154,6 +154,19 @@ config CPU_THERMAL
 
 	  If you want this support, you should say Y here.
 
+config CPU_IDLE_THERMAL
+	tristate "generic cpu idle cooling support"
+	depends on CPU_FREQ
+	help
+	  This implements the generic cpu cooling mechanism through idle
+	  injection.
+
+	  This will throttle cpu by injecting specified idle time in
+	  a fixed cycle. All cpu in same cluster will enter idle synchronously
+	  to reach deepest idle state when injecting idle.
+
+	  If you want this support, you should say Y here.
+
 config CLOCK_THERMAL
 	bool "Generic clock cooling support"
 	depends on COMMON_CLK
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index 094d703..a4db66e 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -26,6 +26,9 @@ thermal_sys-$(CONFIG_CLOCK_THERMAL)	+= clock_cooling.o
 # devfreq cooling
 thermal_sys-$(CONFIG_DEVFREQ_THERMAL) += devfreq_cooling.o
 
+# cpu idle cooling
+obj-$(CONFIG_CPU_IDLE_THERMAL)	+= cpu_idle_cooling.o
+
 # platform thermal drivers
 obj-y				+= broadcom/
 obj-$(CONFIG_QCOM_SPMI_TEMP_ALARM)	+= qcom-spmi-temp-alarm.o
diff --git a/drivers/thermal/cpu_idle_cooling.c b/drivers/thermal/cpu_idle_cooling.c
new file mode 100644
index 0000000..89a15c5
--- /dev/null
+++ b/drivers/thermal/cpu_idle_cooling.c
@@ -0,0 +1,648 @@
+/*
+ *  linux/drivers/thermal/cpu_idle_cooling.c
+ *
+ *  Copyright (C) 2017  Tao Wang <kevin.wangtao@xxxxxxxxxxxxx>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/kernel_stat.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/cpu.h>
+#include <linux/topology.h>
+#include <linux/cpufreq.h>
+#include <linux/cpumask.h>
+#include <linux/cpuidle.h>
+#include <linux/thermal.h>
+#include <linux/sched.h>
+#include <uapi/linux/sched/types.h>
+#include <linux/slab.h>
+#include <linux/tick.h>
+#include <linux/wait.h>
+#include <linux/sched/rt.h>
+
+#define MAX_TARGET_RATIO		(50U)
+
+#define DEFAULT_WINDOW_SIZE		(1)
+#define DEFAULT_DURATION_JIFFIES	(20)
+
+struct cpu_idle_cooling_device {
+	int id;
+	struct thermal_cooling_device *cooling_dev;
+	wait_queue_head_t wait_queue;
+
+	/* The cpu assigned to collect stat and update
+	 * control parameters. default to BSP but BSP
+	 * can be offlined.
+	 */
+	unsigned long control_cpu;
+
+	unsigned int set_target_ratio;
+	unsigned int current_ratio;
+	unsigned int control_ratio;
+	unsigned int duration;
+	unsigned int window_size;
+
+	cpumask_var_t related_cpus;
+	cpumask_var_t injected_cpus;
+	struct list_head node;
+	bool should_skip;
+	bool clamping;
+};
+
+static LIST_HEAD(cpu_idle_cooling_dev_list);
+static DEFINE_PER_CPU(struct task_struct *, idle_injection_thread_ptr);
+static DEFINE_MUTEX(cpu_idle_cooling_lock);
+
+unsigned long idle_time[NR_CPUS] = {0};
+unsigned long time_stamp[NR_CPUS] = {0};
+static enum cpuhp_state hp_state;
+
+#define STORE_PARAM(param, min, max)			\
+static ssize_t store_##param(struct device *dev,	\
+	struct device_attribute *attr,			\
+	const char *buf, size_t count)			\
+{									\
+	unsigned int new_value;						\
+	struct thermal_cooling_device *cdev;				\
+	struct cpu_idle_cooling_device *idle_cooling_dev;		\
+									\
+	if (dev == NULL || attr == NULL)				\
+		return 0;						\
+									\
+	if (kstrtouint(buf, 10, &new_value))				\
+		return -EINVAL;						\
+									\
+	if (new_value > max || new_value < min) {			\
+		pr_err("Out of range %u, between %d-%d\n",		\
+			new_value, min, max);				\
+		return -EINVAL;						\
+	}								\
+									\
+	cdev = container_of(dev, struct thermal_cooling_device, device);\
+	idle_cooling_dev = cdev->devdata;				\
+	idle_cooling_dev->param = new_value;				\
+									\
+	/* make new value visible to other cpus */			\
+	smp_mb();							\
+									\
+	return count;							\
+}
+
+STORE_PARAM(duration, 10, 500);
+STORE_PARAM(window_size, 1, 10);
+
+#define SHOW_PARAM(param)				\
+static ssize_t show_##param(struct device *dev,		\
+	struct device_attribute *attr, char *buf)	\
+{									\
+	struct thermal_cooling_device *cdev;				\
+	struct cpu_idle_cooling_device *idle_cooling_dev;		\
+									\
+	if (dev == NULL || attr == NULL)				\
+		return 0;						\
+									\
+	cdev = container_of(dev, struct thermal_cooling_device, device);\
+	idle_cooling_dev = cdev->devdata;				\
+									\
+	return snprintf(buf, 12UL, "%d\n",				\
+					idle_cooling_dev->param);	\
+}
+
+SHOW_PARAM(duration);
+SHOW_PARAM(window_size);
+
+static DEVICE_ATTR(duration, 0644, show_duration, store_duration);
+static DEVICE_ATTR(window_size, 0644, show_window_size, store_window_size);
+
+static struct cpu_idle_cooling_device *
+get_cpu_idle_cooling_dev(unsigned long cpu)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev;
+
+	list_for_each_entry(idle_cooling_dev,
+		&cpu_idle_cooling_dev_list, node) {
+		if (cpumask_test_cpu(cpu, idle_cooling_dev->related_cpus))
+			return idle_cooling_dev;
+	}
+
+	return NULL;
+}
+
+#define K_P		10
+#define MAX_COMP	10
+static unsigned int get_compensation(unsigned int current_ratio,
+		unsigned int target_ratio, unsigned int control_ratio)
+{
+	unsigned int comp;
+
+	comp = abs(current_ratio - target_ratio) * K_P / 10;
+	if (comp > MAX_COMP)
+		comp = MAX_COMP;
+
+	if (current_ratio > target_ratio) {
+		if (control_ratio > comp)
+			comp = control_ratio - comp;
+		else
+			comp = 1;
+	} else {
+		if (control_ratio + comp < MAX_TARGET_RATIO)
+			comp = control_ratio + comp;
+		else
+			comp = MAX_TARGET_RATIO;
+
+		if (comp > (target_ratio * 6 / 5))
+			comp = target_ratio * 6 / 5;
+	}
+
+	return comp;
+}
+
+static void update_stats(struct cpu_idle_cooling_device *idle_cooling_dev)
+{
+	unsigned long cpu;
+	u64 now, now_idle, delta_time, delta_idle;
+	u64 min_idle_ratio = 100;
+	u64 idle_ratio = 0;
+
+	for_each_cpu(cpu, idle_cooling_dev->related_cpus) {
+		now_idle = get_cpu_idle_time(cpu, &now, 0);
+		delta_idle = now_idle - idle_time[cpu];
+		delta_time = now - time_stamp[cpu];
+		idle_time[cpu] = now_idle;
+		time_stamp[cpu] = now;
+
+		if (delta_idle >= delta_time || !cpu_online(cpu))
+			now_idle = 100;
+		else if (delta_time)
+			now_idle = div64_u64(100 * delta_idle, delta_time);
+		else
+			return;
+
+		if (now_idle < min_idle_ratio)
+			min_idle_ratio = now_idle;
+
+		idle_ratio += now_idle;
+	}
+
+	idle_ratio /= cpumask_weight(idle_cooling_dev->related_cpus);
+	if (idle_ratio > MAX_TARGET_RATIO)
+		idle_ratio = min_idle_ratio;
+
+	if (idle_cooling_dev->should_skip)
+		idle_ratio = (idle_cooling_dev->current_ratio + idle_ratio) / 2;
+
+	idle_cooling_dev->current_ratio = (unsigned int)idle_ratio;
+	idle_cooling_dev->control_ratio = get_compensation(idle_ratio,
+				idle_cooling_dev->set_target_ratio,
+				idle_cooling_dev->control_ratio);
+	idle_cooling_dev->should_skip =
+			(idle_ratio > (2 * idle_cooling_dev->set_target_ratio));
+	/* make new control_ratio and should skip flag visible to other cpus */
+	smp_mb();
+}
+
+static void inject_idle_fn(struct cpu_idle_cooling_device *idle_cooling_dev)
+{
+	long sleeptime, guard;
+	unsigned int interval_ms; /* jiffies to sleep for each attempt */
+	unsigned long target_jiffies;
+	unsigned int duration_ms = idle_cooling_dev->duration;
+	unsigned long duration_jiffies = msecs_to_jiffies(duration_ms);
+
+	guard = DIV_ROUND_UP(duration_jiffies * (90 - MAX_TARGET_RATIO), 100);
+
+	/* align idle time */
+	target_jiffies = roundup(jiffies, duration_jiffies);
+	sleeptime = target_jiffies - jiffies;
+	if (sleeptime < guard)
+		sleeptime += duration_jiffies;
+
+	if (sleeptime > 0)
+		schedule_timeout_interruptible(sleeptime);
+
+	interval_ms = duration_ms * idle_cooling_dev->control_ratio / 100;
+
+	if (idle_cooling_dev->should_skip)
+		return;
+
+	if (interval_ms)
+		play_idle(interval_ms);
+}
+
+static int idle_injection_thread(void *arg)
+{
+	unsigned long cpunr = (unsigned long)arg;
+	struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO/2 };
+	unsigned int count = 0;
+	struct cpu_idle_cooling_device *idle_cooling_dev;
+
+	set_freezable();
+
+	sched_setscheduler(current, SCHED_FIFO, &param);
+
+	mutex_lock(&cpu_idle_cooling_lock);
+	idle_cooling_dev = get_cpu_idle_cooling_dev(cpunr);
+	mutex_unlock(&cpu_idle_cooling_lock);
+
+	while (!kthread_should_stop()) {
+		wait_event_interruptible(idle_cooling_dev->wait_queue,
+			(idle_cooling_dev->clamping && cpu_online(cpunr)) ||
+			kthread_should_stop());
+
+		if (kthread_should_stop())
+			break;
+
+		/* rebind thread to cpu */
+		if (set_cpus_allowed_ptr(current, cpumask_of(cpunr)))
+			continue;
+
+		try_to_freeze();
+
+		while (idle_cooling_dev->clamping &&
+			cpu_online(cpunr)) {
+			try_to_freeze();
+
+			count++;
+			/*
+			 * only elected controlling cpu can collect stats
+			 * and update control parameters.
+			 */
+			if (cpunr == idle_cooling_dev->control_cpu
+				&& !(count % idle_cooling_dev->window_size))
+				update_stats(idle_cooling_dev);
+
+			inject_idle_fn(idle_cooling_dev);
+		}
+	}
+
+	return 0;
+}
+
+static int create_idle_thread(struct cpu_idle_cooling_device *idle_cooling_dev)
+{
+	unsigned long cpu;
+	struct task_struct *thread;
+
+	init_waitqueue_head(&idle_cooling_dev->wait_queue);
+
+	/* start one thread per online cpu */
+	for_each_cpu(cpu, idle_cooling_dev->related_cpus) {
+		thread = kthread_create_on_node(idle_injection_thread,
+						(void *) cpu,
+						cpu_to_node(cpu),
+						"kidle_inject/%lu", cpu);
+		/* bind to cpu here */
+		if (likely(!IS_ERR(thread))) {
+			cpumask_set_cpu(cpu, idle_cooling_dev->injected_cpus);
+			kthread_bind(thread, cpu);
+			wake_up_process(thread);
+			per_cpu(idle_injection_thread_ptr, cpu) = thread;
+		} else {
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+
+static void stop_idle_thread(struct cpu_idle_cooling_device *idle_cooling_dev)
+{
+	unsigned long cpu;
+	struct task_struct **percpu_thread;
+
+	idle_cooling_dev->clamping = false;
+	/*
+	 * make clamping visible to other cpus and give per cpu threads
+	 * sometime to exit, or gets killed later.
+	 */
+	smp_mb();
+	msleep(idle_cooling_dev->duration);
+	for_each_cpu(cpu, idle_cooling_dev->injected_cpus) {
+		pr_debug("idle inject thread for cpu %lu alive, kill\n", cpu);
+		percpu_thread = per_cpu_ptr(&idle_injection_thread_ptr, cpu);
+		if (!IS_ERR_OR_NULL(*percpu_thread)) {
+			kthread_stop(*percpu_thread);
+			*percpu_thread = NULL;
+		}
+		cpumask_clear_cpu(cpu, idle_cooling_dev->injected_cpus);
+	}
+}
+
+static int idle_injection_cpu_online(unsigned int cpu)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev;
+
+	idle_cooling_dev = get_cpu_idle_cooling_dev(cpu);
+	if (idle_cooling_dev) {
+		/* prefer BSP as controlling CPU */
+		if (cpu == cpumask_first(idle_cooling_dev->injected_cpus)
+			|| !cpu_online(idle_cooling_dev->control_cpu)) {
+			idle_cooling_dev->control_cpu = cpu;
+			/* make new control_cpu visible to other cpus */
+			smp_mb();
+		}
+		wake_up_interruptible(&idle_cooling_dev->wait_queue);
+	}
+
+	return 0;
+}
+
+static int idle_injection_cpu_predown(unsigned int cpu)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev;
+
+	idle_cooling_dev = get_cpu_idle_cooling_dev(cpu);
+	if (idle_cooling_dev) {
+		if (cpu == idle_cooling_dev->control_cpu) {
+			cpu = cpumask_next_and(-1,
+				idle_cooling_dev->injected_cpus,
+				cpu_online_mask);
+
+			if (cpu < nr_cpu_ids)
+				idle_cooling_dev->control_cpu = cpu;
+			/* make new control_cpu visible to other cpus */
+			smp_mb();
+		}
+	}
+
+	return 0;
+}
+
+static int idle_get_max_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	*state = MAX_TARGET_RATIO;
+
+	return 0;
+}
+
+static int idle_get_cur_state(struct thermal_cooling_device *cdev,
+				 unsigned long *state)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev = cdev->devdata;
+
+	if (true == idle_cooling_dev->clamping)
+		*state = (unsigned long)idle_cooling_dev->current_ratio;
+	else
+		*state = 0; /* indicates invalid state */
+
+	return 0;
+}
+
+static int idle_set_cur_state(struct thermal_cooling_device *cdev,
+				 unsigned long new_target_ratio)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev = cdev->devdata;
+	int ret = 0;
+
+	mutex_lock(&cdev->lock);
+
+	new_target_ratio = clamp(new_target_ratio, 0UL,
+				(unsigned long) MAX_TARGET_RATIO);
+	if (idle_cooling_dev->set_target_ratio == 0
+		&& new_target_ratio > 0) {
+		idle_cooling_dev->set_target_ratio =
+			(unsigned int) new_target_ratio;
+		idle_cooling_dev->control_ratio =
+			idle_cooling_dev->set_target_ratio;
+		idle_cooling_dev->current_ratio =
+			idle_cooling_dev->set_target_ratio;
+		idle_cooling_dev->clamping = true;
+		wake_up_interruptible(&idle_cooling_dev->wait_queue);
+	} else if (idle_cooling_dev->set_target_ratio > 0) {
+		if (new_target_ratio == 0) {
+			idle_cooling_dev->set_target_ratio = 0;
+			idle_cooling_dev->clamping = false;
+			/* make clamping visible to other cpus */
+			smp_mb();
+		} else	/* adjust currently running */ {
+			idle_cooling_dev->set_target_ratio =
+				(unsigned int) new_target_ratio;
+			/* make new set_target_ratio visible to other cpus */
+			smp_mb();
+		}
+	}
+
+	mutex_unlock(&cdev->lock);
+
+	return ret;
+}
+
+static struct thermal_cooling_device_ops cpu_idle_injection_cooling_ops = {
+	.get_max_state = idle_get_max_state,
+	.get_cur_state = idle_get_cur_state,
+	.set_cur_state = idle_set_cur_state,
+};
+
+unsigned long get_max_idle_state(const struct cpumask *clip_cpus)
+{
+	return MAX_TARGET_RATIO;
+}
+EXPORT_SYMBOL_GPL(get_max_idle_state);
+
+void set_idle_state(const struct cpumask *clip_cpus, unsigned long idle_ratio)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev;
+
+	mutex_lock(&cpu_idle_cooling_lock);
+	list_for_each_entry(idle_cooling_dev,
+		&cpu_idle_cooling_dev_list, node) {
+		if (cpumask_subset(idle_cooling_dev->related_cpus, clip_cpus))
+			idle_set_cur_state(idle_cooling_dev->cooling_dev,
+					idle_ratio);
+	}
+	mutex_unlock(&cpu_idle_cooling_lock);
+}
+EXPORT_SYMBOL_GPL(set_idle_state);
+
+struct thermal_cooling_device * __init
+cpu_idle_cooling_register(const struct cpumask *clip_cpus)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev;
+	struct thermal_cooling_device *ret;
+	unsigned long cpu;
+	char dev_name[THERMAL_NAME_LENGTH];
+
+	if (cpumask_empty(clip_cpus))
+		return ERR_PTR(-ENOMEM);
+
+	mutex_lock(&cpu_idle_cooling_lock);
+	get_online_cpus();
+	list_for_each_entry(idle_cooling_dev,
+		&cpu_idle_cooling_dev_list, node) {
+		if (cpumask_intersects(idle_cooling_dev->related_cpus,
+			clip_cpus)) {
+			ret = ERR_PTR(-EINVAL);
+			goto exit_unlock;
+		}
+	}
+
+	idle_cooling_dev = kzalloc(sizeof(*idle_cooling_dev), GFP_KERNEL);
+	if (!idle_cooling_dev) {
+		ret = ERR_PTR(-ENOMEM);
+		goto exit_unlock;
+	}
+
+	if (!zalloc_cpumask_var(&idle_cooling_dev->related_cpus, GFP_KERNEL)) {
+		ret = ERR_PTR(-ENOMEM);
+		goto exit_free_dev;
+	}
+
+	if (!zalloc_cpumask_var(&idle_cooling_dev->injected_cpus, GFP_KERNEL)) {
+		ret = ERR_PTR(-ENOMEM);
+		goto exit_free_related_cpus;
+	}
+
+	cpumask_copy(idle_cooling_dev->related_cpus, clip_cpus);
+	cpu = cpumask_first(clip_cpus);
+	idle_cooling_dev->control_cpu = cpu;
+	idle_cooling_dev->id = topology_physical_package_id(cpu);
+	idle_cooling_dev->window_size = DEFAULT_WINDOW_SIZE;
+	idle_cooling_dev->duration = jiffies_to_msecs(DEFAULT_DURATION_JIFFIES);
+
+	if (create_idle_thread(idle_cooling_dev)) {
+		ret = ERR_PTR(-ENOMEM);
+		goto exit_free_injected_cpus;
+	}
+
+	snprintf(dev_name, sizeof(dev_name), "thermal-cpuidle-%d",
+		 idle_cooling_dev->id);
+	ret = thermal_cooling_device_register(dev_name,
+					idle_cooling_dev,
+					&cpu_idle_injection_cooling_ops);
+	if (IS_ERR(ret))
+		goto exit_stop_thread;
+
+	idle_cooling_dev->cooling_dev = ret;
+
+	if (device_create_file(&idle_cooling_dev->cooling_dev->device,
+		&dev_attr_duration)) {
+		ret = ERR_PTR(-ENOMEM);
+		goto exit_unregister_cdev;
+	}
+
+	if (device_create_file(&idle_cooling_dev->cooling_dev->device,
+		&dev_attr_window_size)) {
+		ret = ERR_PTR(-ENOMEM);
+		goto exit_remove_duration_attr;
+	}
+
+	list_add(&idle_cooling_dev->node, &cpu_idle_cooling_dev_list);
+
+	goto exit_unlock;
+
+exit_remove_duration_attr:
+	device_remove_file(&idle_cooling_dev->cooling_dev->device,
+			&dev_attr_duration);
+exit_unregister_cdev:
+	thermal_cooling_device_unregister(idle_cooling_dev->cooling_dev);
+exit_stop_thread:
+	stop_idle_thread(idle_cooling_dev);
+exit_free_injected_cpus:
+	free_cpumask_var(idle_cooling_dev->injected_cpus);
+exit_free_related_cpus:
+	free_cpumask_var(idle_cooling_dev->related_cpus);
+exit_free_dev:
+	kfree(idle_cooling_dev);
+exit_unlock:
+	put_online_cpus();
+	mutex_unlock(&cpu_idle_cooling_lock);
+	return ret;
+}
+
+void cpu_idle_cooling_unregister(struct thermal_cooling_device *cdev)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev;
+
+	if (IS_ERR_OR_NULL(cdev))
+		return;
+
+	idle_cooling_dev = cdev->devdata;
+
+	mutex_lock(&cpu_idle_cooling_lock);
+	get_online_cpus();
+	list_del(&idle_cooling_dev->node);
+	put_online_cpus();
+	mutex_unlock(&cpu_idle_cooling_lock);
+
+	device_remove_file(&cdev->device, &dev_attr_window_size);
+	device_remove_file(&cdev->device, &dev_attr_duration);
+	thermal_cooling_device_unregister(idle_cooling_dev->cooling_dev);
+
+	stop_idle_thread(idle_cooling_dev);
+	free_cpumask_var(idle_cooling_dev->injected_cpus);
+	free_cpumask_var(idle_cooling_dev->related_cpus);
+	kfree(idle_cooling_dev);
+}
+
+static void __cpu_idle_cooling_exit(void)
+{
+	struct cpu_idle_cooling_device *idle_cooling_dev;
+
+	while (!list_empty(&cpu_idle_cooling_dev_list)) {
+		idle_cooling_dev = list_first_entry(&cpu_idle_cooling_dev_list,
+				struct cpu_idle_cooling_device, node);
+		cpu_idle_cooling_unregister(idle_cooling_dev->cooling_dev);
+	}
+
+	if (hp_state > 0)
+		cpuhp_remove_state_nocalls(hp_state);
+}
+
+static int __init cpu_idle_cooling_init(void)
+{
+	struct thermal_cooling_device *ret;
+	cpumask_t rest_cpu_mask = CPU_MASK_ALL;
+	const struct cpumask *register_cpu_mask;
+
+	hp_state = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+			"thermal/cpu_idle_cooling:online",
+			idle_injection_cpu_online,
+			idle_injection_cpu_predown);
+	if (hp_state < 0)
+		return hp_state;
+
+	do {
+		register_cpu_mask =
+			topology_core_cpumask(cpumask_first(&rest_cpu_mask));
+
+		if (cpumask_empty(register_cpu_mask))
+			break;
+
+		ret = cpu_idle_cooling_register(register_cpu_mask);
+		if (IS_ERR(ret)) {
+			__cpu_idle_cooling_exit();
+			return -ENOMEM;
+		}
+	} while (cpumask_andnot(&rest_cpu_mask,
+				&rest_cpu_mask,
+				register_cpu_mask));
+
+	return 0;
+}
+module_init(cpu_idle_cooling_init);
+
+static void __exit cpu_idle_cooling_exit(void)
+{
+	__cpu_idle_cooling_exit();
+}
+module_exit(cpu_idle_cooling_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Tao Wang <kevin.wangtao@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("CPU Idle Cooling Driver for ARM Platform");
-- 
1.7.9.5