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Message-ID: <CA+Z25wUJYfsQgXAoqBNb+G=uS8GwCUpgKbG5nDawfATjjhATjA@mail.gmail.com>
Date: Tue, 18 Sep 2012 10:50:34 +0530
From: Rajagopal Venkat <rajagopal.venkat@...aro.org>
To: myungjoo.ham@...sung.com
Cc: "mturquette@...aro.org" <mturquette@...aro.org>,
박경민 <kyungmin.park@...sung.com>,
"rjw@...k.pl" <rjw@...k.pl>,
"patches@...aro.org" <patches@...aro.org>,
"linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH 1/3] devfreq: core updates to support devices which
can idle
On 17 September 2012 17:46, MyungJoo Ham <myungjoo.ham@...sung.com> wrote:
>> On 10 September 2012 14:43, 함명주 <myungjoo.ham@...sung.com> wrote:
>> >> 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();
>>
>> I don't think is the case. The governor can make use of devfreq->lock if needed.
>> Anyways, I have revised locking mechanism in v2 set.
>>
>> > Or at least, userspace_init and userspace_exit functions require mutex_lock.
>>
>> The userspace_init function is executed only when device is added to devfreq
>> framework. This function itself is creating sysfs attributes. So this should not
>> be a concern for us.
>>
>> The userspace_exit is executed when device is removed from devfreq
>> framework. sysfs_remove_group() should take care of serving any pending
>> reference to sysfs attributes before removing them. No concern here as well.
>> Am I missing something which demand locking for these functions?
>>
>> > Event_handler callback won't want the properties in devfreq to be changed externally during its execution.
>>
>> Agree.
>
> If so, the GOV_INTERVAL handler of ondemand requires mutex_lock.
> (and probably, nested mutex lock for monitor_resume)
>
I don't think so. The polling_ms value update and the GOV_INTERVAL
event are handled in store_polling_interval() i.e same caller's context. So
no reason for concern here. Also polling_ms value update and queuing
the work(using polling_ms) are synchronized.
> It determins next action based on the value protected by the
> devfreq lock. It won't crash the kernel and it won't happen
> often. However, it may behave incorrectly.
>
> Why don't we simply let the all the struct devfreq protected
> when the external code (governors) is probably reading/writing the
> protected values?
>
> This also guarantees that the event handler gets the exact status
> modified by the event caller. Otherwise, the event handler may
> get status different from the event caller's intention.
>
>
> Cheers!
> MyungJoo
>
>
>>
>> >
>> > Plus, please edit Documentation/ABI entry (central_polling is being removed)
>> Done.
>> >
>> > Other than that, it looks fine.
>> >
>> > Cheers!
>> > MyungJoo
>> >
>> >>
>> >> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@...aro.org>
>> >> ---
>> >> 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
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>>
>>
>>
>> --
>> Regards,
>> Rajagopal
>>
>>
>>
>>
>>
>>
>>
--
Regards,
Rajagopal
--
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