Date:   Tue, 6 Jun 2017 09:11:35 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Tao Wang <kevin.wangtao@...ilicon.com>
Cc:     rui.zhang@...el.com, edubezval@...il.com, amit.kachhap@...il.com,
        javi.merino@...nel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, sunzhaosheng@...ilicon.com,
        vincent.guittot@...aro.org, jean.wangtao@...aro.org,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH RFC 1/2] thermal/cpu idle cooling: Introduce cpu idle
 cooling driver

+ Daniel

On 05-06-17, 17:07, Tao Wang wrote:
> 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@...ilicon.com>
> ---
>  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@...ilicon.com>
> + *
> + *  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@...ilicon.com>");
> +MODULE_DESCRIPTION("CPU Idle Cooling Driver for ARM Platform");
> -- 
> 1.7.9.5

-- 
viresh

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