[PATCH 0/3] devfreq: Add support for devices which can idle

[PATCH 0/3] devfreq: Add support for devices which can idle

[Rajagopal Venkat]

This patchset updates devfreq core to add support for devices
which can idle. When device idleness is detected perhaps
through runtime-pm, need some mechanism to suspend devfreq
load monitoring and resume when device is back online.

patch 1 introduce core design changes - per device work, decouple
delayed work from core and event based interaction.
patch 2 add devfreq suspend and resume apis.
patch 3 current frequency bug fix and add new sysfs attribute for
governor predicted next target frequency.

The existing devfreq apis are kept intact. Two new apis
devfreq_suspend_device() and devfreq_resume_device() are
added to support suspend/resume of device devfreq.

--
Rajagopal Venkat (3):
  devfreq: core updates to support devices which can idle
  devfreq: Add suspend and resume apis
  devfreq: Add current freq callback in device profile

 Documentation/ABI/testing/sysfs-class-devfreq |   7 +
 drivers/devfreq/devfreq.c                     | 412 +++++++++++---------------
 drivers/devfreq/governor.h                    |  11 +
 drivers/devfreq/governor_performance.c        |  16 +-
 drivers/devfreq/governor_powersave.c          |  16 +-
 drivers/devfreq/governor_simpleondemand.c     |  42 +++
 drivers/devfreq/governor_userspace.c          |  23 +-
 include/linux/devfreq.h                       |  46 ++-
 8 files changed, 291 insertions(+), 282 deletions(-)

-- 
1.7.11.3

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

[Rajagopal Venkat]

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.

Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.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

[PATCH 2/3] devfreq: Add suspend and resume apis

[Rajagopal Venkat]

Add devfreq suspend/resume apis for devfreq users. This patch
supports suspend and resume of devfreq load monitoring, required
for devices which can idle.

Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
---
 drivers/devfreq/devfreq.c                 | 26 ++++++++++++++++++++++++++
 drivers/devfreq/governor.h                |  2 ++
 drivers/devfreq/governor_simpleondemand.c |  9 +++++++++
 include/linux/devfreq.h                   | 12 ++++++++++++
 4 files changed, 49 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index be524c7..3a5f126 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -365,6 +365,32 @@ int devfreq_remove_device(struct devfreq *devfreq)
 }
 EXPORT_SYMBOL(devfreq_remove_device);
 
+/**
+ * devfreq_suspend_device() - Suspend devfreq of a device.
+ * @devfreq	the devfreq instance to be suspended
+ */
+int devfreq_suspend_device(struct devfreq *devfreq)
+{
+	if (!devfreq)
+		return -EINVAL;
+
+	return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_SUSPEND);
+}
+EXPORT_SYMBOL(devfreq_suspend_device);
+
+/**
+ * devfreq_resume_device() - Resume devfreq of a device.
+ * @devfreq	the devfreq instance to be resumed
+ */
+int devfreq_resume_device(struct devfreq *devfreq)
+{
+	if (!devfreq)
+		return -EINVAL;
+
+	return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_RESUME);
+}
+EXPORT_SYMBOL(devfreq_resume_device);
+
 static ssize_t show_governor(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
index 4a86af7..7dbbdfc 100644
--- a/drivers/devfreq/governor.h
+++ b/drivers/devfreq/governor.h
@@ -22,6 +22,8 @@
 #define DEVFREQ_GOV_START			0x1
 #define DEVFREQ_GOV_STOP			0x2
 #define DEVFREQ_GOV_INTERVAL			0x3
+#define DEVFREQ_GOV_SUSPEND			0x4
+#define DEVFREQ_GOV_RESUME			0x5
 
 /* Caution: devfreq->lock must be locked before calling update_devfreq */
 extern int update_devfreq(struct devfreq *devfreq);
diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
index 9802bf9..35b8e8e 100644
--- a/drivers/devfreq/governor_simpleondemand.c
+++ b/drivers/devfreq/governor_simpleondemand.c
@@ -113,6 +113,15 @@ int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
 		else
 			ret = devfreq_monitor_resume(devfreq);
 		break;
+
+	case DEVFREQ_GOV_SUSPEND:
+		ret = devfreq_monitor_suspend(devfreq);
+		break;
+
+	case DEVFREQ_GOV_RESUME:
+		ret = devfreq_monitor_resume(devfreq);
+		break;
+
 	default:
 		break;
 	}
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 7a11c3e..7c7e179 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -155,6 +155,8 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
 				  const struct devfreq_governor *governor,
 				  void *data);
 extern int devfreq_remove_device(struct devfreq *devfreq);
+extern int devfreq_suspend_device(struct devfreq *devfreq);
+extern int devfreq_resume_device(struct devfreq *devfreq);
 
 /* Helper functions for devfreq user device driver with OPP. */
 extern struct opp *devfreq_recommended_opp(struct device *dev,
@@ -208,6 +210,16 @@ static int devfreq_remove_device(struct devfreq *devfreq)
 	return 0;
 }
 
+static int devfreq_suspend_device(struct devfreq *devfreq)
+{
+	return 0;
+}
+
+static int devfreq_resume_device(struct devfreq *devfreq)
+{
+	return 0;
+}
+
 static struct opp *devfreq_recommended_opp(struct device *dev,
 					   unsigned long *freq, u32 flags)
 {
-- 
1.7.11.3

[PATCH 3/3] devfreq: Add current freq callback in device profile

[Rajagopal Venkat]

Devfreq returns governor predicted frequency as current
frequency via sysfs interface. But device may not support
all frequencies that governor predicts. Its driver
responsibility to maintain current frequency at which device
is operating. Add a callback in device profile to fix this.
Also add a new sysfs node to expose governor predicted next
target frequency.

Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
---
 Documentation/ABI/testing/sysfs-class-devfreq |  7 +++++++
 drivers/devfreq/devfreq.c                     | 14 ++++++++++++++
 include/linux/devfreq.h                       |  3 +++
 3 files changed, 24 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
index 23d78b5..9df5205 100644
--- a/Documentation/ABI/testing/sysfs-class-devfreq
+++ b/Documentation/ABI/testing/sysfs-class-devfreq
@@ -21,6 +21,13 @@ Description:
 		The /sys/class/devfreq/.../cur_freq shows the current
 		frequency of the corresponding devfreq object.
 
+What:		/sys/class/devfreq/.../target_freq
+Date:		September 2012
+Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+		The /sys/class/devfreq/.../target_freq shows the next governor
+		predicted target frequency of the corresponding devfreq object.
+
 What:		/sys/class/devfreq/.../central_polling
 Date:		September 2011
 Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 3a5f126..55e9046 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -400,6 +400,19 @@ static ssize_t show_governor(struct device *dev,
 static ssize_t show_freq(struct device *dev,
 			 struct device_attribute *attr, char *buf)
 {
+	unsigned long freq;
+	struct devfreq *devfreq = to_devfreq(dev);
+
+	if (devfreq->profile->get_cur_freq)
+		if (!devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
+			return sprintf(buf, "%lu\n", freq);
+
+	return sprintf(buf, "<unknown>");
+}
+
+static ssize_t show_target_freq(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
 	return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
 }
 
@@ -503,6 +516,7 @@ 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(target_freq, S_IRUGO, show_target_freq, 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),
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 7c7e179..d12ed41 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -66,6 +66,8 @@ struct devfreq_dev_status {
  *			explained above with "DEVFREQ_FLAG_*" macros.
  * @get_dev_status	The device should provide the current performance
  *			status to devfreq, which is used by governors.
+ * @get_cur_freq	The device should provide the current frequency
+ *			at which it is operating.
  * @exit		An optional callback that is called when devfreq
  *			is removing the devfreq object due to error or
  *			from devfreq_remove_device() call. If the user
@@ -79,6 +81,7 @@ struct devfreq_dev_profile {
 	int (*target)(struct device *dev, unsigned long *freq, u32 flags);
 	int (*get_dev_status)(struct device *dev,
 			      struct devfreq_dev_status *stat);
+	int (*get_cur_freq)(struct device *dev, unsigned long *freq);
 	void (*exit)(struct device *dev);
 };
 
-- 
1.7.11.3

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

[Rafael J. Wysocki]

On Monday, September 03, 2012, Rajagopal Venkat 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.
> 
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>

This one looks like a nice simplification.  I wonder if everyone in the CC list
is fine with it?

One remark below.

> ---
>  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.
> + */

It would be good to say in the kerneldoc comment what the idea is, because it
is not particularly clear from the code.  In particular, why can't
devfreq_monitor_suspend() be the same as devfreq_monitor_stop()?

> +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.

It would be good to explain the idea here too.

> + */
> +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;
> +}

Thanks,
Rafael

Re: [PATCH 2/3] devfreq: Add suspend and resume apis

[Rafael J. Wysocki]

On Monday, September 03, 2012, Rajagopal Venkat wrote:
> Add devfreq suspend/resume apis for devfreq users. This patch
> supports suspend and resume of devfreq load monitoring, required
> for devices which can idle.
> 
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>

I'd call the new functions devfreq_dev_suspend() and devfreq_dev_resume(),
respectively, because the names you're using currently suggest that the
device itself is suspended/resumed, which isn't the case.

Thanks,
Rafael


> ---
>  drivers/devfreq/devfreq.c                 | 26 ++++++++++++++++++++++++++
>  drivers/devfreq/governor.h                |  2 ++
>  drivers/devfreq/governor_simpleondemand.c |  9 +++++++++
>  include/linux/devfreq.h                   | 12 ++++++++++++
>  4 files changed, 49 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index be524c7..3a5f126 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -365,6 +365,32 @@ int devfreq_remove_device(struct devfreq *devfreq)
>  }
>  EXPORT_SYMBOL(devfreq_remove_device);
>  
> +/**
> + * devfreq_suspend_device() - Suspend devfreq of a device.
> + * @devfreq	the devfreq instance to be suspended
> + */
> +int devfreq_suspend_device(struct devfreq *devfreq)
> +{
> +	if (!devfreq)
> +		return -EINVAL;
> +
> +	return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_SUSPEND);
> +}
> +EXPORT_SYMBOL(devfreq_suspend_device);
> +
> +/**
> + * devfreq_resume_device() - Resume devfreq of a device.
> + * @devfreq	the devfreq instance to be resumed
> + */
> +int devfreq_resume_device(struct devfreq *devfreq)
> +{
> +	if (!devfreq)
> +		return -EINVAL;
> +
> +	return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_RESUME);
> +}
> +EXPORT_SYMBOL(devfreq_resume_device);
> +
>  static ssize_t show_governor(struct device *dev,
>  			     struct device_attribute *attr, char *buf)
>  {
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index 4a86af7..7dbbdfc 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -22,6 +22,8 @@
>  #define DEVFREQ_GOV_START			0x1
>  #define DEVFREQ_GOV_STOP			0x2
>  #define DEVFREQ_GOV_INTERVAL			0x3
> +#define DEVFREQ_GOV_SUSPEND			0x4
> +#define DEVFREQ_GOV_RESUME			0x5
>  
>  /* Caution: devfreq->lock must be locked before calling update_devfreq */
>  extern int update_devfreq(struct devfreq *devfreq);
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index 9802bf9..35b8e8e 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -113,6 +113,15 @@ int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
>  		else
>  			ret = devfreq_monitor_resume(devfreq);
>  		break;
> +
> +	case DEVFREQ_GOV_SUSPEND:
> +		ret = devfreq_monitor_suspend(devfreq);
> +		break;
> +
> +	case DEVFREQ_GOV_RESUME:
> +		ret = devfreq_monitor_resume(devfreq);
> +		break;
> +
>  	default:
>  		break;
>  	}
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 7a11c3e..7c7e179 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -155,6 +155,8 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
>  				  const struct devfreq_governor *governor,
>  				  void *data);
>  extern int devfreq_remove_device(struct devfreq *devfreq);
> +extern int devfreq_suspend_device(struct devfreq *devfreq);
> +extern int devfreq_resume_device(struct devfreq *devfreq);
>  
>  /* Helper functions for devfreq user device driver with OPP. */
>  extern struct opp *devfreq_recommended_opp(struct device *dev,
> @@ -208,6 +210,16 @@ static int devfreq_remove_device(struct devfreq *devfreq)
>  	return 0;
>  }
>  
> +static int devfreq_suspend_device(struct devfreq *devfreq)
> +{
> +	return 0;
> +}
> +
> +static int devfreq_resume_device(struct devfreq *devfreq)
> +{
> +	return 0;
> +}
> +
>  static struct opp *devfreq_recommended_opp(struct device *dev,
>  					   unsigned long *freq, u32 flags)
>  {
> 

Re: [PATCH 3/3] devfreq: Add current freq callback in device profile

[Rafael J. Wysocki]

On Monday, September 03, 2012, Rajagopal Venkat wrote:
> Devfreq returns governor predicted frequency as current
> frequency via sysfs interface. But device may not support
> all frequencies that governor predicts.

Do you have any examples, even out of the tree?

> Its driver
> responsibility to maintain current frequency at which device
> is operating. Add a callback in device profile to fix this.

Obviously, there are no users of this callback in the tree right now, so it
may not be regarded as a fix.  I'd rather say it's a new mechanism for
drivers to use if their current frequencies differ from the governor-selected
ones.

> Also add a new sysfs node to expose governor predicted next
> target frequency.
> 
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
> ---
>  Documentation/ABI/testing/sysfs-class-devfreq |  7 +++++++
>  drivers/devfreq/devfreq.c                     | 14 ++++++++++++++
>  include/linux/devfreq.h                       |  3 +++
>  3 files changed, 24 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
> index 23d78b5..9df5205 100644
> --- a/Documentation/ABI/testing/sysfs-class-devfreq
> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
> @@ -21,6 +21,13 @@ Description:
>  		The /sys/class/devfreq/.../cur_freq shows the current
>  		frequency of the corresponding devfreq object.
>  
> +What:		/sys/class/devfreq/.../target_freq
> +Date:		September 2012
> +Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>

It's a bit odd to add someone else as a contact for interfaces that you're
introducing.  I'd need MyungJoo Ham's ACK for that.

> +Description:
> +		The /sys/class/devfreq/.../target_freq shows the next governor
> +		predicted target frequency of the corresponding devfreq object.
> +
>  What:		/sys/class/devfreq/.../central_polling
>  Date:		September 2011
>  Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 3a5f126..55e9046 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -400,6 +400,19 @@ static ssize_t show_governor(struct device *dev,
>  static ssize_t show_freq(struct device *dev,
>  			 struct device_attribute *attr, char *buf)
>  {
> +	unsigned long freq;
> +	struct devfreq *devfreq = to_devfreq(dev);
> +
> +	if (devfreq->profile->get_cur_freq)
> +		if (!devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))

That should be

+	if (devfreq->profile->get_cur_freq
+	    && !devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))

> +			return sprintf(buf, "%lu\n", freq);
> +

Moreover, I suppose it should fall back to the current behavior if
.get_cur_freq() is not present.

> +	return sprintf(buf, "<unknown>");
> +}
> +
> +static ssize_t show_target_freq(struct device *dev,
> +			struct device_attribute *attr, char *buf)
> +{
>  	return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
>  }
>  
> @@ -503,6 +516,7 @@ 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(target_freq, S_IRUGO, show_target_freq, 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),
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 7c7e179..d12ed41 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -66,6 +66,8 @@ struct devfreq_dev_status {
>   *			explained above with "DEVFREQ_FLAG_*" macros.
>   * @get_dev_status	The device should provide the current performance
>   *			status to devfreq, which is used by governors.
> + * @get_cur_freq	The device should provide the current frequency
> + *			at which it is operating.
>   * @exit		An optional callback that is called when devfreq
>   *			is removing the devfreq object due to error or
>   *			from devfreq_remove_device() call. If the user
> @@ -79,6 +81,7 @@ struct devfreq_dev_profile {
>  	int (*target)(struct device *dev, unsigned long *freq, u32 flags);
>  	int (*get_dev_status)(struct device *dev,
>  			      struct devfreq_dev_status *stat);
> +	int (*get_cur_freq)(struct device *dev, unsigned long *freq);
>  	void (*exit)(struct device *dev);
>  };

Thanks,
Rafael

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

[Rajagopal Venkat]

On 10 September 2012 03:16, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Monday, September 03, 2012, Rajagopal Venkat 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.
>>
>> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
>
> This one looks like a nice simplification.  I wonder if everyone in the CC list
> is fine with it?
>
> One remark below.
>
>> ---
>>  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.
>> + */
>
> It would be good to say in the kerneldoc comment what the idea is, because it
> is not particularly clear from the code.  In particular, why can't
> devfreq_monitor_suspend() be the same as devfreq_monitor_stop()?
Ok. Kerneldoc comment will be added here.

The idea is,
devfreq_monitor_suspend() - called to suspend device devfreq during device
idleness.

devfreq_monitor_stop() - called when device is removed from the devfreq
framework.

Though these two functions can be same, intentionally I kept them separate
to provide hooks for collecting transition statistics.

>
>> +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.
>
> It would be good to explain the idea here too.
Ok. Done.

>
>> + */
>> +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;
>> +}
>
> Thanks,
> Rafael
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Regards,
Rajagopal

Re: [PATCH 2/3] devfreq: Add suspend and resume apis

[Rajagopal Venkat]

On 10 September 2012 03:21, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Monday, September 03, 2012, Rajagopal Venkat wrote:
>> Add devfreq suspend/resume apis for devfreq users. This patch
>> supports suspend and resume of devfreq load monitoring, required
>> for devices which can idle.
>>
>> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
>
> I'd call the new functions devfreq_dev_suspend() and devfreq_dev_resume(),
> respectively, because the names you're using currently suggest that the
> device itself is suspended/resumed, which isn't the case.

devfreq_add_device() and devfreq_remove_device() are two existing APIs.

I did follow same naming pattern to maintain uniformity and introduced
devfreq_suspend_device() and devfreq_resume_device() functions.

Do you suggest to follow devfreq_dev_xxx pattern even for existing APIs?

>
> Thanks,
> Rafael
>
>
>> ---
>>  drivers/devfreq/devfreq.c                 | 26 ++++++++++++++++++++++++++
>>  drivers/devfreq/governor.h                |  2 ++
>>  drivers/devfreq/governor_simpleondemand.c |  9 +++++++++
>>  include/linux/devfreq.h                   | 12 ++++++++++++
>>  4 files changed, 49 insertions(+)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index be524c7..3a5f126 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -365,6 +365,32 @@ int devfreq_remove_device(struct devfreq *devfreq)
>>  }
>>  EXPORT_SYMBOL(devfreq_remove_device);
>>
>> +/**
>> + * devfreq_suspend_device() - Suspend devfreq of a device.
>> + * @devfreq  the devfreq instance to be suspended
>> + */
>> +int devfreq_suspend_device(struct devfreq *devfreq)
>> +{
>> +     if (!devfreq)
>> +             return -EINVAL;
>> +
>> +     return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_SUSPEND);
>> +}
>> +EXPORT_SYMBOL(devfreq_suspend_device);
>> +
>> +/**
>> + * devfreq_resume_device() - Resume devfreq of a device.
>> + * @devfreq  the devfreq instance to be resumed
>> + */
>> +int devfreq_resume_device(struct devfreq *devfreq)
>> +{
>> +     if (!devfreq)
>> +             return -EINVAL;
>> +
>> +     return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_RESUME);
>> +}
>> +EXPORT_SYMBOL(devfreq_resume_device);
>> +
>>  static ssize_t show_governor(struct device *dev,
>>                            struct device_attribute *attr, char *buf)
>>  {
>> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
>> index 4a86af7..7dbbdfc 100644
>> --- a/drivers/devfreq/governor.h
>> +++ b/drivers/devfreq/governor.h
>> @@ -22,6 +22,8 @@
>>  #define DEVFREQ_GOV_START                    0x1
>>  #define DEVFREQ_GOV_STOP                     0x2
>>  #define DEVFREQ_GOV_INTERVAL                 0x3
>> +#define DEVFREQ_GOV_SUSPEND                  0x4
>> +#define DEVFREQ_GOV_RESUME                   0x5
>>
>>  /* Caution: devfreq->lock must be locked before calling update_devfreq */
>>  extern int update_devfreq(struct devfreq *devfreq);
>> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
>> index 9802bf9..35b8e8e 100644
>> --- a/drivers/devfreq/governor_simpleondemand.c
>> +++ b/drivers/devfreq/governor_simpleondemand.c
>> @@ -113,6 +113,15 @@ int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
>>               else
>>                       ret = devfreq_monitor_resume(devfreq);
>>               break;
>> +
>> +     case DEVFREQ_GOV_SUSPEND:
>> +             ret = devfreq_monitor_suspend(devfreq);
>> +             break;
>> +
>> +     case DEVFREQ_GOV_RESUME:
>> +             ret = devfreq_monitor_resume(devfreq);
>> +             break;
>> +
>>       default:
>>               break;
>>       }
>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>> index 7a11c3e..7c7e179 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -155,6 +155,8 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
>>                                 const struct devfreq_governor *governor,
>>                                 void *data);
>>  extern int devfreq_remove_device(struct devfreq *devfreq);
>> +extern int devfreq_suspend_device(struct devfreq *devfreq);
>> +extern int devfreq_resume_device(struct devfreq *devfreq);
>>
>>  /* Helper functions for devfreq user device driver with OPP. */
>>  extern struct opp *devfreq_recommended_opp(struct device *dev,
>> @@ -208,6 +210,16 @@ static int devfreq_remove_device(struct devfreq *devfreq)
>>       return 0;
>>  }
>>
>> +static int devfreq_suspend_device(struct devfreq *devfreq)
>> +{
>> +     return 0;
>> +}
>> +
>> +static int devfreq_resume_device(struct devfreq *devfreq)
>> +{
>> +     return 0;
>> +}
>> +
>>  static struct opp *devfreq_recommended_opp(struct device *dev,
>>                                          unsigned long *freq, u32 flags)
>>  {
>>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Regards,
Rajagopal

Re: [PATCH 3/3] devfreq: Add current freq callback in device profile

[Rajagopal Venkat]

On 10 September 2012 03:30, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Monday, September 03, 2012, Rajagopal Venkat wrote:
>> Devfreq returns governor predicted frequency as current
>> frequency via sysfs interface. But device may not support
>> all frequencies that governor predicts.
>
> Do you have any examples, even out of the tree?
The exynos4_bus.c devfreq driver supports five opps. But the ondemand
governor can suggest any frequency between min and max(assuming
policy is set). As per design, governors only need to provide recommended
frequency and the corresponding driver will interpret it correctly.

So, the governor recommended frequency and the frequency at which
device is running could be different. This patch attempts to add new sysfs
node for exposing device current running frequency.
>
>> Its driver
>> responsibility to maintain current frequency at which device
>> is operating. Add a callback in device profile to fix this.
>
> Obviously, there are no users of this callback in the tree right now, so it
> may not be regarded as a fix.  I'd rather say it's a new mechanism for
> drivers to use if their current frequencies differ from the governor-selected
> ones.
Ok. It will be updated in next version.

>
>> Also add a new sysfs node to expose governor predicted next
>> target frequency.
>>
>> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
>> ---
>>  Documentation/ABI/testing/sysfs-class-devfreq |  7 +++++++
>>  drivers/devfreq/devfreq.c                     | 14 ++++++++++++++
>>  include/linux/devfreq.h                       |  3 +++
>>  3 files changed, 24 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
>> index 23d78b5..9df5205 100644
>> --- a/Documentation/ABI/testing/sysfs-class-devfreq
>> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
>> @@ -21,6 +21,13 @@ Description:
>>               The /sys/class/devfreq/.../cur_freq shows the current
>>               frequency of the corresponding devfreq object.
>>
>> +What:                /sys/class/devfreq/.../target_freq
>> +Date:                September 2012
>> +Contact:     MyungJoo Ham <myungjoo.ham@samsung.com>
>
> It's a bit odd to add someone else as a contact for interfaces that you're
> introducing.  I'd need MyungJoo Ham's ACK for that.
>
>> +Description:
>> +             The /sys/class/devfreq/.../target_freq shows the next governor
>> +             predicted target frequency of the corresponding devfreq object.
>> +
>>  What:                /sys/class/devfreq/.../central_polling
>>  Date:                September 2011
>>  Contact:     MyungJoo Ham <myungjoo.ham@samsung.com>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 3a5f126..55e9046 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -400,6 +400,19 @@ static ssize_t show_governor(struct device *dev,
>>  static ssize_t show_freq(struct device *dev,
>>                        struct device_attribute *attr, char *buf)
>>  {
>> +     unsigned long freq;
>> +     struct devfreq *devfreq = to_devfreq(dev);
>> +
>> +     if (devfreq->profile->get_cur_freq)
>> +             if (!devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
>
> That should be
>
> +       if (devfreq->profile->get_cur_freq
> +           && !devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
Done.

>
>> +                     return sprintf(buf, "%lu\n", freq);
>> +
>
> Moreover, I suppose it should fall back to the current behavior if
> .get_cur_freq() is not present.
Agree. Done.

>
>> +     return sprintf(buf, "<unknown>");
>> +}
>> +
>> +static ssize_t show_target_freq(struct device *dev,
>> +                     struct device_attribute *attr, char *buf)
>> +{
>>       return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
>>  }
>>
>> @@ -503,6 +516,7 @@ 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(target_freq, S_IRUGO, show_target_freq, 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),
>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>> index 7c7e179..d12ed41 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -66,6 +66,8 @@ struct devfreq_dev_status {
>>   *                   explained above with "DEVFREQ_FLAG_*" macros.
>>   * @get_dev_status   The device should provide the current performance
>>   *                   status to devfreq, which is used by governors.
>> + * @get_cur_freq     The device should provide the current frequency
>> + *                   at which it is operating.
>>   * @exit             An optional callback that is called when devfreq
>>   *                   is removing the devfreq object due to error or
>>   *                   from devfreq_remove_device() call. If the user
>> @@ -79,6 +81,7 @@ struct devfreq_dev_profile {
>>       int (*target)(struct device *dev, unsigned long *freq, u32 flags);
>>       int (*get_dev_status)(struct device *dev,
>>                             struct devfreq_dev_status *stat);
>> +     int (*get_cur_freq)(struct device *dev, unsigned long *freq);
>>       void (*exit)(struct device *dev);
>>  };
>
> Thanks,
> Rafael



-- 
Regards,
Rajagopal

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

[Rafael J. Wysocki]

On Monday, September 10, 2012, Rajagopal Venkat wrote:
> On 10 September 2012 03:16, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > On Monday, September 03, 2012, Rajagopal Venkat 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.
> >>
> >> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
> >
> > This one looks like a nice simplification.  I wonder if everyone in the CC list
> > is fine with it?
> >
> > One remark below.
> >
> >> ---
> >>  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.
> >> + */
> >
> > It would be good to say in the kerneldoc comment what the idea is, because it
> > is not particularly clear from the code.  In particular, why can't
> > devfreq_monitor_suspend() be the same as devfreq_monitor_stop()?
> Ok. Kerneldoc comment will be added here.
> 
> The idea is,
> devfreq_monitor_suspend() - called to suspend device devfreq during device
> idleness.
> 
> devfreq_monitor_stop() - called when device is removed from the devfreq
> framework.
> 
> Though these two functions can be same, intentionally I kept them separate
> to provide hooks for collecting transition statistics.

In that case it looks like there is a race below:

> >> +int devfreq_monitor_suspend(struct devfreq *devfreq)
> >> +{
> >> +     int ret = -EPERM;
> >> +
> >> +     if (delayed_work_pending(&devfreq->work)) {

Don't you need to check the timer here too?  It is possible that the work
isn't pending yet, but the timer has already been set.

> >> +             cancel_delayed_work_sync(&devfreq->work);
> >> +             ret = 0;
> >> +     }
> >> +
> >> +     return ret;
> >> +}

BTW, why do you want to return -EPERM on error?

Rafael

Re: [PATCH 2/3] devfreq: Add suspend and resume apis

[MyungJoo Ham]

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> Add devfreq suspend/resume apis for devfreq users. This patch
> supports suspend and resume of devfreq load monitoring, required
> for devices which can idle.
> 
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>

Rather than letting device driver be responsible to call devfreq_suspend_device() or devfreq_dev_suspend(),would there be any problems in using pm notifier here? (calling the event handler with DEVFREQ_GOV_SUSPEND/RESUME at pm notifier, stopping them earlier and resuming tham later)

What devfreq-core and devfreq-governors do with suspend/resume is handling the delayed workqueue and it does not have anything to do with device-specific tasks. Thus, having each device driver handle device-specifics with its own pm_ops and having devfreq-core stop sampling seem appropriate.

Putting another burden to each device driver (to call devfreq_suspend/resume_device() at its pm_ops) for an obvious task that could be done at core doesn't seem fair.

Thank you.



Cheers!
MyungJoo

> ---
>  drivers/devfreq/devfreq.c                 | 26 ++++++++++++++++++++++++++
>  drivers/devfreq/governor.h                |  2 ++
>  drivers/devfreq/governor_simpleondemand.c |  9 +++++++++
>  include/linux/devfreq.h                   | 12 ++++++++++++
>  4 files changed, 49 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index be524c7..3a5f126 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -365,6 +365,32 @@ int devfreq_remove_device(struct devfreq *devfreq)
>  }
>  EXPORT_SYMBOL(devfreq_remove_device);
>  
> +/**
> + * devfreq_suspend_device() - Suspend devfreq of a device.
> + * @devfreq	the devfreq instance to be suspended
> + */
> +int devfreq_suspend_device(struct devfreq *devfreq)
> +{
> +	if (!devfreq)
> +		return -EINVAL;
> +
> +	return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_SUSPEND);
> +}
> +EXPORT_SYMBOL(devfreq_suspend_device);
> +
> +/**
> + * devfreq_resume_device() - Resume devfreq of a device.
> + * @devfreq	the devfreq instance to be resumed
> + */
> +int devfreq_resume_device(struct devfreq *devfreq)
> +{
> +	if (!devfreq)
> +		return -EINVAL;
> +
> +	return devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_RESUME);
> +}
> +EXPORT_SYMBOL(devfreq_resume_device);
> +
>  static ssize_t show_governor(struct device *dev,
>  			     struct device_attribute *attr, char *buf)
>  {
> diff --git a/drivers/devfreq/governor.h b/drivers/devfreq/governor.h
> index 4a86af7..7dbbdfc 100644
> --- a/drivers/devfreq/governor.h
> +++ b/drivers/devfreq/governor.h
> @@ -22,6 +22,8 @@
>  #define DEVFREQ_GOV_START			0x1
>  #define DEVFREQ_GOV_STOP			0x2
>  #define DEVFREQ_GOV_INTERVAL			0x3
> +#define DEVFREQ_GOV_SUSPEND			0x4
> +#define DEVFREQ_GOV_RESUME			0x5
>  
>  /* Caution: devfreq->lock must be locked before calling update_devfreq */
>  extern int update_devfreq(struct devfreq *devfreq);
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index 9802bf9..35b8e8e 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -113,6 +113,15 @@ int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
>  		else
>  			ret = devfreq_monitor_resume(devfreq);
>  		break;
> +
> +	case DEVFREQ_GOV_SUSPEND:
> +		ret = devfreq_monitor_suspend(devfreq);
> +		break;
> +
> +	case DEVFREQ_GOV_RESUME:
> +		ret = devfreq_monitor_resume(devfreq);
> +		break;
> +
>  	default:
>  		break;
>  	}
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 7a11c3e..7c7e179 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -155,6 +155,8 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
>  				  const struct devfreq_governor *governor,
>  				  void *data);
>  extern int devfreq_remove_device(struct devfreq *devfreq);
> +extern int devfreq_suspend_device(struct devfreq *devfreq);
> +extern int devfreq_resume_device(struct devfreq *devfreq);
>  
>  /* Helper functions for devfreq user device driver with OPP. */
>  extern struct opp *devfreq_recommended_opp(struct device *dev,
> @@ -208,6 +210,16 @@ static int devfreq_remove_device(struct devfreq *devfreq)
>  	return 0;
>  }
>  
> +static int devfreq_suspend_device(struct devfreq *devfreq)
> +{
> +	return 0;
> +}
> +
> +static int devfreq_resume_device(struct devfreq *devfreq)
> +{
> +	return 0;
> +}
> +
>  static struct opp *devfreq_recommended_opp(struct device *dev,
>  					   unsigned long *freq, u32 flags)
>  {
> -- 
> 1.7.11.3
> 
> 
> 
> 
>        
>   
>          
> 
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