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Message-id: <28328998.110941347946468804.JavaMail.weblogic@epml02>
Date: Tue, 18 Sep 2012 05:34:32 +0000 (GMT)
From: MyungJoo Ham <myungjoo.ham@...sung.com>
To: Rajagopal Venkat <rajagopal.venkat@...aro.org>
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: Re: [PATCH 1/3] devfreq: core updates to support devices which
can idle
> Sender : Rajagopal Venkat<rajagopal.venkat@...aro.org>
> Date : 2012-09-18 14:20 (GMT+09:00)
> Title : Re: Re: [PATCH 1/3] devfreq: core updates to support devices which can idle
> On 17 September 2012 17:46, MyungJoo Ham wrote:
> >> On 10 September 2012 14:43, 함명주 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.
The proposed structure in this patch is:
[mutex_lock]
update value
[mutex_unlock]
...
[mutex_lock]
use the updated value (including queueing the work)
[mutex_unlock]
It is not synchronized.
If it is to be synchronized, the mutex should be kept locked.
Besides, as mentioned below, in order to guarantee that the modified
values related with an event trigger are kept intact for the event
handlers, you need to keep the mutex locked. It may be a neglectible
issue if we only consider polling_ms; however, we should never assume
so because we can have custom governors and drivers. (or even more
events are to be defined later)
Please note that even if every devfreq driver implement mutex-lock/unlock
appropriately, the consistency is not guaranteed as there is unlocked
period between "update" and "read". Assuming that we are to support
run-time governor changes and additional events later as discussed before,
we'd better prepare this beforehand.
>
> > 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
> >> >> ---
> >> >> 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
> >> >> #include
> >> >> #include
> >> >> +#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
>
>
>
>
>
> --
>
> MyungJoo Ham (함명주), PHD
>
> System S/W Lab, S/W Platform Team, Software Center
> Samsung Electronics
> Cell: +82-10-6714-2858
>
>
>
>
>
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