Re: [PATCH 1/3] devfreq: core updates to support devices which can idle

From: 함명주
Date: Mon Sep 10 2012 - 05:13:15 EST


> Prepare devfreq core framework to support devices which
> can idle. When device idleness is detected perhaps through
> runtime-pm, need some mechanism to suspend devfreq load
> monitoring and resume back when device is online. Present
> code continues monitoring unless device is removed from
> devfreq core.
>
> This patch introduces following design changes,
>
> - use per device work instead of global work to monitor device
> load. This enables suspend/resume of device devfreq and
> reduces monitoring code complexity.
> - decouple delayed work based load monitoring logic from core
> by introducing helpers functions to be used by governors. This
> provides flexibility for governors either to use delayed work
> based monitoring functions or to implement their own mechanism.
> - devfreq core interacts with governors via events to perform
> specific actions. These events include start/stop devfreq.
> This sets ground for adding suspend/resume events.
>
> The devfreq apis are not modified and are kept intact.

Hello,

Please revise locking mechanism along with event handler.

It appears that we need to do mutex_lock(&devfreq->lock) before calling devfreq->governor->event_handler();
Or at least, userspace_init and userspace_exit functions require mutex_lock.
Event_handler callback won't want the properties in devfreq to be changed externally during its execution.

Plus, please edit Documentation/ABI entry (central_polling is being removed)

Other than that, it looks fine.

Cheers!
MyungJoo

>
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@xxxxxxxxxx>
> ---
> drivers/devfreq/devfreq.c | 376 ++++++++++--------------------
> drivers/devfreq/governor.h | 9 +
> drivers/devfreq/governor_performance.c | 16 +-
> drivers/devfreq/governor_powersave.c | 16 +-
> drivers/devfreq/governor_simpleondemand.c | 33 +++
> drivers/devfreq/governor_userspace.c | 23 +-
> include/linux/devfreq.h | 31 +--
> 7 files changed, 220 insertions(+), 284 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index b146d76..be524c7 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -30,17 +30,11 @@
> struct class *devfreq_class;
>
> /*
> - * devfreq_work periodically monitors every registered device.
> - * The minimum polling interval is one jiffy. The polling interval is
> - * determined by the minimum polling period among all polling devfreq
> - * devices. The resolution of polling interval is one jiffy.
> + * devfreq core provides delayed work based load monitoring helper
> + * functions. Governors can use these or can implement their own
> + * monitoring mechanism.
> */
> -static bool polling;
> static struct workqueue_struct *devfreq_wq;
> -static struct delayed_work devfreq_work;
> -
> -/* wait removing if this is to be removed */
> -static struct devfreq *wait_remove_device;
>
> /* The list of all device-devfreq */
> static LIST_HEAD(devfreq_list);
> @@ -72,6 +66,8 @@ static struct devfreq *find_device_devfreq(struct device *dev)
> return ERR_PTR(-ENODEV);
> }
>
> +/* Load monitoring helper functions for governors use */
> +
> /**
> * update_devfreq() - Reevaluate the device and configure frequency.
> * @devfreq: the devfreq instance.
> @@ -121,6 +117,90 @@ int update_devfreq(struct devfreq *devfreq)
> }
>
> /**
> + * devfreq_monitor() - Periodically poll devfreq objects.
> + * @work: the work struct used to run devfreq_monitor periodically.
> + *
> + */
> +static void devfreq_monitor(struct work_struct *work)
> +{
> + int err;
> + struct devfreq *devfreq = container_of(work,
> + struct devfreq, work.work);
> +
> + mutex_lock(&devfreq->lock);
> + err = update_devfreq(devfreq);
> + mutex_unlock(&devfreq->lock);
> + if (err)
> + dev_err(&devfreq->dev, "dvfs failed with (%d) error\n", err);
> +
> + queue_delayed_work(devfreq_wq, &devfreq->work,
> + msecs_to_jiffies(devfreq->profile->polling_ms));
> +}
> +
> +/**
> + * devfreq_monitor_start() - Start load monitoring of devfreq instance
> + * using default delayed work
> + * @devfreq: the devfreq instance.
> + *
> + * Returns 0 if monitoring started, non-zero otherwise.
> + * Note: This function is exported for governors.
> + */
> +int devfreq_monitor_start(struct devfreq *devfreq)
> +{
> + INIT_DEFERRABLE_WORK(&devfreq->work, devfreq_monitor);
> + return !queue_delayed_work(devfreq_wq, &devfreq->work,
> + msecs_to_jiffies(devfreq->profile->polling_ms));
> +}
> +
> +/**
> + * devfreq_monitor_stop() - Stop load monitoring of a devfreq instance
> + * @devfreq: the devfreq instance.
> + *
> + * Note: This function is exported for governors.
> + */
> +void devfreq_monitor_stop(struct devfreq *devfreq)
> +{
> + cancel_delayed_work_sync(&devfreq->work);
> +}
> +
> +/**
> + * devfreq_monitor_suspend() - Suspend load monitoring of a devfreq instance
> + * @devfreq: the devfreq instance.
> + *
> + * Note: This function is exported for governors.
> + */
> +int devfreq_monitor_suspend(struct devfreq *devfreq)
> +{
> + int ret = -EPERM;
> +
> + if (delayed_work_pending(&devfreq->work)) {
> + cancel_delayed_work_sync(&devfreq->work);
> + ret = 0;
> + }
> +
> + return ret;
> +}
> +
> +/**
> + * devfreq_monitor_resume() - Resume load monitoring of a devfreq instance
> + * @devfreq: the devfreq instance.
> + *
> + * Returns 0 if monitoring re-started, non-zero otherwise.
> + * Note: This function is exported for governors.
> + */
> +int devfreq_monitor_resume(struct devfreq *devfreq)
> +{
> + int ret = -EPERM;
> +
> + if (!delayed_work_pending(&devfreq->work)) {
> + ret = !queue_delayed_work(devfreq_wq, &devfreq->work,
> + msecs_to_jiffies(devfreq->profile->polling_ms));
> + }
> +
> + return ret;
> +}
> +
> +/**
> * devfreq_notifier_call() - Notify that the device frequency requirements
> * has been changed out of devfreq framework.
> * @nb the notifier_block (supposed to be devfreq->nb)
> @@ -143,59 +223,33 @@ static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
> }
>
> /**
> - * _remove_devfreq() - Remove devfreq from the device.
> + * _remove_devfreq() - Remove devfreq from the devfreq list and
> + release its resources.
> * @devfreq: the devfreq struct
> * @skip: skip calling device_unregister().
> - *
> - * Note that the caller should lock devfreq->lock before calling
> - * this. _remove_devfreq() will unlock it and free devfreq
> - * internally. devfreq_list_lock should be locked by the caller
> - * as well (not relased at return)
> - *
> - * Lock usage:
> - * devfreq->lock: locked before call.
> - * unlocked at return (and freed)
> - * devfreq_list_lock: locked before call.
> - * kept locked at return.
> - * if devfreq is centrally polled.
> - *
> - * Freed memory:
> - * devfreq
> */
> static void _remove_devfreq(struct devfreq *devfreq, bool skip)
> {
> - if (!mutex_is_locked(&devfreq->lock)) {
> - WARN(true, "devfreq->lock must be locked by the caller.\n");
> - return;
> - }
> - if (!devfreq->governor->no_central_polling &&
> - !mutex_is_locked(&devfreq_list_lock)) {
> - WARN(true, "devfreq_list_lock must be locked by the caller.\n");
> + mutex_lock(&devfreq_list_lock);
> + if (IS_ERR(find_device_devfreq(devfreq->dev.parent))) {
> + mutex_unlock(&devfreq_list_lock);
> + dev_warn(&devfreq->dev, "releasing devfreq which doesn't exist\n");
> return;
> }
> + list_del(&devfreq->node);
> + mutex_unlock(&devfreq_list_lock);
>
> - if (devfreq->being_removed)
> - return;
> -
> - devfreq->being_removed = true;
> + devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_STOP);
>
> if (devfreq->profile->exit)
> devfreq->profile->exit(devfreq->dev.parent);
>
> - if (devfreq->governor->exit)
> - devfreq->governor->exit(devfreq);
> -
> if (!skip && get_device(&devfreq->dev)) {
> device_unregister(&devfreq->dev);
> put_device(&devfreq->dev);
> }
>
> - if (!devfreq->governor->no_central_polling)
> - list_del(&devfreq->node);
> -
> - mutex_unlock(&devfreq->lock);
> mutex_destroy(&devfreq->lock);
> -
> kfree(devfreq);
> }
>
> @@ -210,130 +264,8 @@ static void _remove_devfreq(struct devfreq *devfreq, bool skip)
> static void devfreq_dev_release(struct device *dev)
> {
> struct devfreq *devfreq = to_devfreq(dev);
> - bool central_polling = !devfreq->governor->no_central_polling;
> -
> - /*
> - * If devfreq_dev_release() was called by device_unregister() of
> - * _remove_devfreq(), we cannot mutex_lock(&devfreq->lock) and
> - * being_removed is already set. This also partially checks the case
> - * where devfreq_dev_release() is called from a thread other than
> - * the one called _remove_devfreq(); however, this case is
> - * dealt completely with another following being_removed check.
> - *
> - * Because being_removed is never being
> - * unset, we do not need to worry about race conditions on
> - * being_removed.
> - */
> - if (devfreq->being_removed)
> - return;
> -
> - if (central_polling)
> - mutex_lock(&devfreq_list_lock);
> -
> - mutex_lock(&devfreq->lock);
> -
> - /*
> - * Check being_removed flag again for the case where
> - * devfreq_dev_release() was called in a thread other than the one
> - * possibly called _remove_devfreq().
> - */
> - if (devfreq->being_removed) {
> - mutex_unlock(&devfreq->lock);
> - goto out;
> - }
>
> - /* devfreq->lock is unlocked and removed in _removed_devfreq() */
> _remove_devfreq(devfreq, true);
> -
> -out:
> - if (central_polling)
> - mutex_unlock(&devfreq_list_lock);
> -}
> -
> -/**
> - * devfreq_monitor() - Periodically poll devfreq objects.
> - * @work: the work struct used to run devfreq_monitor periodically.
> - *
> - */
> -static void devfreq_monitor(struct work_struct *work)
> -{
> - static unsigned long last_polled_at;
> - struct devfreq *devfreq, *tmp;
> - int error;
> - unsigned long jiffies_passed;
> - unsigned long next_jiffies = ULONG_MAX, now = jiffies;
> - struct device *dev;
> -
> - /* Initially last_polled_at = 0, polling every device at bootup */
> - jiffies_passed = now - last_polled_at;
> - last_polled_at = now;
> - if (jiffies_passed == 0)
> - jiffies_passed = 1;
> -
> - mutex_lock(&devfreq_list_lock);
> - list_for_each_entry_safe(devfreq, tmp, &devfreq_list, node) {
> - mutex_lock(&devfreq->lock);
> - dev = devfreq->dev.parent;
> -
> - /* Do not remove tmp for a while */
> - wait_remove_device = tmp;
> -
> - if (devfreq->governor->no_central_polling ||
> - devfreq->next_polling == 0) {
> - mutex_unlock(&devfreq->lock);
> - continue;
> - }
> - mutex_unlock(&devfreq_list_lock);
> -
> - /*
> - * Reduce more next_polling if devfreq_wq took an extra
> - * delay. (i.e., CPU has been idled.)
> - */
> - if (devfreq->next_polling <= jiffies_passed) {
> - error = update_devfreq(devfreq);
> -
> - /* Remove a devfreq with an error. */
> - if (error && error != -EAGAIN) {
> -
> - dev_err(dev, "Due to update_devfreq error(%d), devfreq(%s) is removed from the device\n",
> - error, devfreq->governor->name);
> -
> - /*
> - * Unlock devfreq before locking the list
> - * in order to avoid deadlock with
> - * find_device_devfreq or others
> - */
> - mutex_unlock(&devfreq->lock);
> - mutex_lock(&devfreq_list_lock);
> - /* Check if devfreq is already removed */
> - if (IS_ERR(find_device_devfreq(dev)))
> - continue;
> - mutex_lock(&devfreq->lock);
> - /* This unlocks devfreq->lock and free it */
> - _remove_devfreq(devfreq, false);
> - continue;
> - }
> - devfreq->next_polling = devfreq->polling_jiffies;
> - } else {
> - devfreq->next_polling -= jiffies_passed;
> - }
> -
> - if (devfreq->next_polling)
> - next_jiffies = (next_jiffies > devfreq->next_polling) ?
> - devfreq->next_polling : next_jiffies;
> -
> - mutex_unlock(&devfreq->lock);
> - mutex_lock(&devfreq_list_lock);
> - }
> - wait_remove_device = NULL;
> - mutex_unlock(&devfreq_list_lock);
> -
> - if (next_jiffies > 0 && next_jiffies < ULONG_MAX) {
> - polling = true;
> - queue_delayed_work(devfreq_wq, &devfreq_work, next_jiffies);
> - } else {
> - polling = false;
> - }
> }
>
> /**
> @@ -357,16 +289,13 @@ struct devfreq *devfreq_add_device(struct device *dev,
> return ERR_PTR(-EINVAL);
> }
>
> -
> - if (!governor->no_central_polling) {
> - mutex_lock(&devfreq_list_lock);
> - devfreq = find_device_devfreq(dev);
> - mutex_unlock(&devfreq_list_lock);
> - if (!IS_ERR(devfreq)) {
> - dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
> - err = -EINVAL;
> - goto err_out;
> - }
> + mutex_lock(&devfreq_list_lock);
> + devfreq = find_device_devfreq(dev);
> + mutex_unlock(&devfreq_list_lock);
> + if (!IS_ERR(devfreq)) {
> + dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
> + err = -EINVAL;
> + goto err_out;
> }
>
> devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
> @@ -386,48 +315,40 @@ struct devfreq *devfreq_add_device(struct device *dev,
> devfreq->governor = governor;
> devfreq->previous_freq = profile->initial_freq;
> devfreq->data = data;
> - devfreq->next_polling = devfreq->polling_jiffies
> - = msecs_to_jiffies(devfreq->profile->polling_ms);
> devfreq->nb.notifier_call = devfreq_notifier_call;
>
> dev_set_name(&devfreq->dev, dev_name(dev));
> err = device_register(&devfreq->dev);
> if (err) {
> put_device(&devfreq->dev);
> + mutex_unlock(&devfreq->lock);
> goto err_dev;
> }
>
> - if (governor->init)
> - err = governor->init(devfreq);
> - if (err)
> - goto err_init;
> -
> mutex_unlock(&devfreq->lock);
>
> - if (governor->no_central_polling)
> - goto out;
> -
> mutex_lock(&devfreq_list_lock);
> -
> list_add(&devfreq->node, &devfreq_list);
> + mutex_unlock(&devfreq_list_lock);
>
> - if (devfreq_wq && devfreq->next_polling && !polling) {
> - polling = true;
> - queue_delayed_work(devfreq_wq, &devfreq_work,
> - devfreq->next_polling);
> + err = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_START);
> + if (err) {
> + dev_err(dev, "%s: Unable to start governor for the device\n",
> + __func__);
> + goto err_init;
> }
> - mutex_unlock(&devfreq_list_lock);
> -out:
> +
> return devfreq;
>
> err_init:
> + list_del(&devfreq->node);
> device_unregister(&devfreq->dev);
> err_dev:
> - mutex_unlock(&devfreq->lock);
> kfree(devfreq);
> err_out:
> return ERR_PTR(err);
> }
> +EXPORT_SYMBOL(devfreq_add_device);
>
> /**
> * devfreq_remove_device() - Remove devfreq feature from a device.
> @@ -435,30 +356,14 @@ err_out:
> */
> int devfreq_remove_device(struct devfreq *devfreq)
> {
> - bool central_polling;
> -
> if (!devfreq)
> return -EINVAL;
>
> - central_polling = !devfreq->governor->no_central_polling;
> -
> - if (central_polling) {
> - mutex_lock(&devfreq_list_lock);
> - while (wait_remove_device == devfreq) {
> - mutex_unlock(&devfreq_list_lock);
> - schedule();
> - mutex_lock(&devfreq_list_lock);
> - }
> - }
> -
> - mutex_lock(&devfreq->lock);
> - _remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */
> -
> - if (central_polling)
> - mutex_unlock(&devfreq_list_lock);
> + _remove_devfreq(devfreq, false);
>
> return 0;
> }
> +EXPORT_SYMBOL(devfreq_remove_device);
>
> static ssize_t show_governor(struct device *dev,
> struct device_attribute *attr, char *buf)
> @@ -492,33 +397,15 @@ static ssize_t store_polling_interval(struct device *dev,
>
> mutex_lock(&df->lock);
> df->profile->polling_ms = value;
> - df->next_polling = df->polling_jiffies
> - = msecs_to_jiffies(value);
> mutex_unlock(&df->lock);
>
> + df->governor->event_handler(df, DEVFREQ_GOV_INTERVAL);
> ret = count;
>
> - if (df->governor->no_central_polling)
> - goto out;
> -
> - mutex_lock(&devfreq_list_lock);
> - if (df->next_polling > 0 && !polling) {
> - polling = true;
> - queue_delayed_work(devfreq_wq, &devfreq_work,
> - df->next_polling);
> - }
> - mutex_unlock(&devfreq_list_lock);
> out:
> return ret;
> }
>
> -static ssize_t show_central_polling(struct device *dev,
> - struct device_attribute *attr, char *buf)
> -{
> - return sprintf(buf, "%d\n",
> - !to_devfreq(dev)->governor->no_central_polling);
> -}
> -
> static ssize_t store_min_freq(struct device *dev, struct device_attribute *attr,
> const char *buf, size_t count)
> {
> @@ -590,7 +477,6 @@ static ssize_t show_max_freq(struct device *dev, struct device_attribute *attr,
> static struct device_attribute devfreq_attrs[] = {
> __ATTR(governor, S_IRUGO, show_governor, NULL),
> __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
> - __ATTR(central_polling, S_IRUGO, show_central_polling, NULL),
> __ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
> store_polling_interval),
> __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),
> @@ -598,23 +484,6 @@ static struct device_attribute devfreq_attrs[] = {
> { },
> };
>
> -/**
> - * devfreq_start_polling() - Initialize data structure for devfreq framework and
> - * start polling registered devfreq devices.
> - */
> -static int __init devfreq_start_polling(void)
> -{
> - mutex_lock(&devfreq_list_lock);
> - polling = false;
> - devfreq_wq = create_freezable_workqueue("devfreq_wq");
> - INIT_DEFERRABLE_WORK(&devfreq_work, devfreq_monitor);
> - mutex_unlock(&devfreq_list_lock);
> -
> - devfreq_monitor(&devfreq_work.work);
> - return 0;
> -}
> -late_initcall(devfreq_start_polling);
> -
> static int __init devfreq_init(void)
> {
> devfreq_class = class_create(THIS_MODULE, "devfreq");
> @@ -622,7 +491,15 @@ static int __init devfreq_init(void)
> pr_err("%s: couldn't create class\n", __FILE__);
> return PTR_ERR(devfreq_class);
> }
> +
> + devfreq_wq = create_freezable_workqueue("devfreq_wq");
> + if (IS_ERR(devfreq_wq)) {
> + class_destroy(devfreq_class);
> + pr_err("%s: couldn't create workqueue\n", __FILE__);
> + return PTR_ERR(devfreq_wq);
> + }
> devfreq_class->dev_attrs = devfreq_attrs;
> +
> return 0;
> }
> subsys_initcall(devfreq_init);
> @@ -630,6 +507,7 @@ subsys_initcall(devfreq_init);
> static void __exit devfreq_exit(void)
> {
> class_destroy(devfreq_class);
> + destroy_workqueue(devfreq_wq);
> }
> module_exit(devfreq_exit);
>
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index ea7f13c..4a86af7 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -18,7 +18,16 @@
>
> #define to_devfreq(DEV) container_of((DEV), struct devfreq, dev)
>
> +/* Devfreq events */
> +#define DEVFREQ_GOV_START 0x1
> +#define DEVFREQ_GOV_STOP 0x2
> +#define DEVFREQ_GOV_INTERVAL 0x3
> +
> /* Caution: devfreq->lock must be locked before calling update_devfreq */
> extern int update_devfreq(struct devfreq *devfreq);
>
> +extern int devfreq_monitor_start(struct devfreq *devfreq);
> +extern void devfreq_monitor_stop(struct devfreq *devfreq);
> +extern int devfreq_monitor_suspend(struct devfreq *devfreq);
> +extern int devfreq_monitor_resume(struct devfreq *devfreq);
> #endif /* _GOVERNOR_H */
> diff --git a/drivers/devfreq/governor_performance.c b/drivers/devfreq/governor_performance.c
> index af75ddd..b657eff 100644
> --- a/drivers/devfreq/governor_performance.c
> +++ b/drivers/devfreq/governor_performance.c
> @@ -26,14 +26,22 @@ static int devfreq_performance_func(struct devfreq *df,
> return 0;
> }
>
> -static int performance_init(struct devfreq *devfreq)
> +static int devfreq_performance_handler(struct devfreq *devfreq,
> + unsigned int event)
> {
> - return update_devfreq(devfreq);
> + int ret = 0;
> +
> + if (event == DEVFREQ_GOV_START) {
> + mutex_lock(&devfreq->lock);
> + ret = update_devfreq(devfreq);
> + mutex_unlock(&devfreq->lock);
> + }
> +
> + return ret;
> }
>
> const struct devfreq_governor devfreq_performance = {
> .name = "performance",
> - .init = performance_init,
> .get_target_freq = devfreq_performance_func,
> - .no_central_polling = true,
> + .event_handler = devfreq_performance_handler,
> };
> diff --git a/drivers/devfreq/governor_powersave.c b/drivers/devfreq/governor_powersave.c
> index fec0cdb..daa5732 100644
> --- a/drivers/devfreq/governor_powersave.c
> +++ b/drivers/devfreq/governor_powersave.c
> @@ -23,14 +23,22 @@ static int devfreq_powersave_func(struct devfreq *df,
> return 0;
> }
>
> -static int powersave_init(struct devfreq *devfreq)
> +static int devfreq_powersave_handler(struct devfreq *devfreq,
> + unsigned int event)
> {
> - return update_devfreq(devfreq);
> + int ret = 0;
> +
> + if (event == DEVFREQ_GOV_START) {
> + mutex_lock(&devfreq->lock);
> + ret = update_devfreq(devfreq);
> + mutex_unlock(&devfreq->lock);
> + }
> +
> + return ret;
> }
>
> const struct devfreq_governor devfreq_powersave = {
> .name = "powersave",
> - .init = powersave_init,
> .get_target_freq = devfreq_powersave_func,
> - .no_central_polling = true,
> + .event_handler = devfreq_powersave_handler,
> };
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index a2e3eae..9802bf9 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -12,6 +12,7 @@
> #include <linux/errno.h>
> #include <linux/devfreq.h>
> #include <linux/math64.h>
> +#include "governor.h"
>
> /* Default constants for DevFreq-Simple-Ondemand (DFSO) */
> #define DFSO_UPTHRESHOLD (90)
> @@ -88,7 +89,39 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> return 0;
> }
>
> +int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
> + unsigned int event)
> +{
> + int ret = 0;
> +
> + switch (event) {
> + case DEVFREQ_GOV_START:
> + ret = devfreq_monitor_start(devfreq);
> + break;
> +
> + case DEVFREQ_GOV_STOP:
> + devfreq_monitor_stop(devfreq);
> + break;
> +
> + case DEVFREQ_GOV_INTERVAL:
> + /*
> + * if polling interval is set to zero, stop monitoring.
> + * otherwise resume load monitoring.
> + */
> + if (!devfreq->profile->polling_ms)
> + ret = devfreq_monitor_suspend(devfreq);
> + else
> + ret = devfreq_monitor_resume(devfreq);
> + break;
> + default:
> + break;
> + }
> +
> + return ret;
> +}
> +
> const struct devfreq_governor devfreq_simple_ondemand = {
> .name = "simple_ondemand",
> .get_target_freq = devfreq_simple_ondemand_func,
> + .event_handler = devfreq_simple_ondemand_handler,
> };
> diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
> index 0681246..c48fca0 100644
> --- a/drivers/devfreq/governor_userspace.c
> +++ b/drivers/devfreq/governor_userspace.c
> @@ -116,10 +116,27 @@ static void userspace_exit(struct devfreq *devfreq)
> devfreq->data = NULL;
> }
>
> +int devfreq_userspace_handler(struct devfreq *devfreq,
> + unsigned int event)
> +{
> + int ret = 0;
> +
> + switch (event) {
> + case DEVFREQ_GOV_START:
> + ret = userspace_init(devfreq);
> + break;
> + case DEVFREQ_GOV_STOP:
> + userspace_exit(devfreq);
> + break;
> + default:
> + break;
> + }
> +
> + return ret;
> +}
> +
> const struct devfreq_governor devfreq_userspace = {
> .name = "userspace",
> .get_target_freq = devfreq_userspace_func,
> - .init = userspace_init,
> - .exit = userspace_exit,
> - .no_central_polling = true,
> + .event_handler = devfreq_userspace_handler,
> };
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 281c72a..7a11c3e 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -91,25 +91,17 @@ struct devfreq_dev_profile {
> * status of the device (load = busy_time / total_time).
> * If no_central_polling is set, this callback is called
> * only with update_devfreq() notified by OPP.
> - * @init Called when the devfreq is being attached to a device
> - * @exit Called when the devfreq is being removed from a
> - * device. Governor should stop any internal routines
> - * before return because related data may be
> - * freed after exit().
> - * @no_central_polling Do not use devfreq's central polling mechanism.
> - * When this is set, devfreq will not call
> - * get_target_freq with devfreq_monitor(). However,
> - * devfreq will call get_target_freq with
> - * devfreq_update() notified by OPP framework.
> + * @event_handler Callback for devfreq core framework to notify events
> + * to governors. Events include per device governor
> + * init and exit, opp changes out of devfreq, suspend
> + * and resume of per device devfreq during device idle.
> *
> * Note that the callbacks are called with devfreq->lock locked by devfreq.
> */
> struct devfreq_governor {
> const char name[DEVFREQ_NAME_LEN];
> int (*get_target_freq)(struct devfreq *this, unsigned long *freq);
> - int (*init)(struct devfreq *this);
> - void (*exit)(struct devfreq *this);
> - const bool no_central_polling;
> + int (*event_handler)(struct devfreq *devfreq, unsigned int event);
> };
>
> /**
> @@ -124,16 +116,10 @@ struct devfreq_governor {
> * @nb notifier block used to notify devfreq object that it should
> * reevaluate operable frequencies. Devfreq users may use
> * devfreq.nb to the corresponding register notifier call chain.
> - * @polling_jiffies interval in jiffies.
> + * @work delayed work for load monitoring.
> * @previous_freq previously configured frequency value.
> - * @next_polling the number of remaining jiffies to poll with
> - * "devfreq_monitor" executions to reevaluate
> - * frequency/voltage of the device. Set by
> - * profile's polling_ms interval.
> * @data Private data of the governor. The devfreq framework does not
> * touch this.
> - * @being_removed a flag to mark that this object is being removed in
> - * order to prevent trying to remove the object multiple times.
> * @min_freq Limit minimum frequency requested by user (0: none)
> * @max_freq Limit maximum frequency requested by user (0: none)
> *
> @@ -153,15 +139,12 @@ struct devfreq {
> struct devfreq_dev_profile *profile;
> const struct devfreq_governor *governor;
> struct notifier_block nb;
> + struct delayed_work work;
>
> - unsigned long polling_jiffies;
> unsigned long previous_freq;
> - unsigned int next_polling;
>
> void *data; /* private data for governors */
>
> - bool being_removed;
> -
> unsigned long min_freq;
> unsigned long max_freq;
> };
> --
> 1.7.11.3
>
>
>
>
>
>
>
>
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