===================================================================
@@ -208,3 +208,17 @@ config APM_EMULATION
random kernel OOPSes or reboots that don't seem to be related to
anything, try disabling/enabling this option (or disabling/enabling
APM in your BIOS).
+
+config PM_RUNTIME
+ bool "Run-time PM core functionality"
+ depends on PM
+ ---help---
+ Enable functionality allowing I/O devices to be put into energy-saving
+ (low power) states at run time (or autosuspended) after a specified
+ period of inactivity and woken up in response to a hardware-generated
+ wake-up event or a driver's request.
+
+ Hardware support is generally required for this functionality to work
+ and the bus type drivers of the buses the devices are on are
+ responsible for the actual handling of the autosuspend requests and
+ wake-up events.
===================================================================
@@ -11,6 +11,7 @@
#include <linux/kobject.h>
#include <linux/string.h>
#include <linux/resume-trace.h>
+#include <linux/workqueue.h>
#include "power.h"
@@ -217,8 +218,24 @@ static struct attribute_group attr_group
.attrs = g,
};
+#ifdef CONFIG_PM_RUNTIME
+struct workqueue_struct *pm_wq;
+
+static int __init pm_start_workqueue(void)
+{
+ pm_wq = create_freezeable_workqueue("pm");
+
+ return pm_wq ? 0 : -ENOMEM;
+}
+#else
+static inline int pm_start_workqueue(void) { return 0; }
+#endif
+
static int __init pm_init(void)
{
+ int error = pm_start_workqueue();
+ if (error)
+ return error;
power_kobj = kobject_create_and_add("power", NULL);
if (!power_kobj)
return -ENOMEM;
===================================================================
@@ -22,6 +22,10 @@
#define _LINUX_PM_H
#include <linux/list.h>
+#include <linux/workqueue.h>
+#include <linux/spinlock.h>
+#include <linux/wait.h>
+#include <linux/timer.h>
/*
* Callbacks for platform drivers to implement.
@@ -165,6 +169,28 @@ typedef struct pm_message {
* It is allowed to unregister devices while the above callbacks are being
* executed. However, it is not allowed to unregister a device from within any
* of its own callbacks.
+ *
+ * There also are the following callbacks related to run-time power management
+ * of devices:
+ *
+ * @runtime_suspend: Prepare the device for a condition in which it won't be
+ * able to communicate with the CPU(s) and RAM due to power management.
+ * This need not mean that the device should be put into a low power state.
+ * For example, if the device is behind a link which is about to be turned
+ * off, the device may remain at full power. If the device does go to low
+ * power and if device_may_wakeup(dev) is true, remote wake-up (i.e., a
+ * hardware mechanism allowing the device to request a change of its power
+ * state, such as PCI PME) should be enabled for it.
+ *
+ * @runtime_resume: Put the device into the fully active state in response to a
+ * wake-up event generated by hardware or at the request of software. If
+ * necessary, put the device into the full power state and restore its
+ * registers, so that it is fully operational.
+ *
+ * @runtime_idle: Device appears to be inactive and it might be put into a low
+ * power state if all of the necessary conditions are satisfied. Check
+ * these conditions and handle the device as appropriate, possibly queueing
+ * a suspend request for it.
*/
struct dev_pm_ops {
@@ -182,6 +208,9 @@ struct dev_pm_ops {
int (*thaw_noirq)(struct device *dev);
int (*poweroff_noirq)(struct device *dev);
int (*restore_noirq)(struct device *dev);
+ int (*runtime_suspend)(struct device *dev);
+ int (*runtime_resume)(struct device *dev);
+ void (*runtime_idle)(struct device *dev);
};
/**
@@ -315,14 +344,81 @@ enum dpm_state {
DPM_OFF_IRQ,
};
+/**
+ * Device run-time power management status.
+ *
+ * These status labels are used internally by the PM core to indicate the
+ * current status of a device with respect to the PM core operations. They do
+ * not reflect the actual power state of the device or its status as seen by the
+ * driver.
+ *
+ * RPM_ACTIVE Device is fully operational. Indicates that the device
+ * bus type's ->runtime_resume() callback has completed
+ * successfully.
+ *
+ * RPM_SUSPENDED Device bus type's ->runtime_suspend() callback has
+ * completed successfully. The device is regarded as
+ * suspended.
+ *
+ * RPM_RESUMING Device bus type's ->runtime_resume() callback is being
+ * executed.
+ *
+ * RPM_SUSPENDING Device bus type's ->runtime_suspend() callback is being
+ * executed.
+ */
+
+enum rpm_status {
+ RPM_ACTIVE = 0,
+ RPM_RESUMING,
+ RPM_SUSPENDED,
+ RPM_SUSPENDING,
+};
+
+/**
+ * Device run-time power management request types.
+ *
+ * RPM_REQ_NONE Do nothing.
+ *
+ * RPM_REQ_IDLE Run the device bus type's ->runtime_idle() callback
+ *
+ * RPM_REQ_SUSPEND Run the device bus type's ->runtime_suspend() callback
+ *
+ * RPM_REQ_RESUME Run the device bus type's ->runtime_resume() callback
+ */
+
+enum rpm_request {
+ RPM_REQ_NONE = 0,
+ RPM_REQ_IDLE,
+ RPM_REQ_SUSPEND,
+ RPM_REQ_RESUME,
+};
+
struct dev_pm_info {
pm_message_t power_state;
- unsigned can_wakeup:1;
- unsigned should_wakeup:1;
+ unsigned int can_wakeup:1;
+ unsigned int should_wakeup:1;
enum dpm_state status; /* Owned by the PM core */
-#ifdef CONFIG_PM_SLEEP
+#ifdef CONFIG_PM_SLEEP
struct list_head entry;
#endif
+#ifdef CONFIG_PM_RUNTIME
+ struct timer_list suspend_timer;
+ unsigned long timer_expires;
+ struct work_struct work;
+ wait_queue_head_t wait_queue;
+ spinlock_t lock;
+ atomic_t usage_count;
+ atomic_t child_count;
+ unsigned int disable_depth:3;
+ unsigned int ignore_children:1;
+ unsigned int runtime_failure:1;
+ unsigned int idle_notification:1;
+ unsigned int request_pending:1;
+ unsigned int deferred_resume:1;
+ enum rpm_request request;
+ enum rpm_status runtime_status;
+ int last_error;
+#endif
};
/*
===================================================================
@@ -1,5 +1,6 @@
obj-$(CONFIG_PM) += sysfs.o
obj-$(CONFIG_PM_SLEEP) += main.o
+obj-$(CONFIG_PM_RUNTIME) += runtime.o
obj-$(CONFIG_PM_TRACE_RTC) += trace.o
ccflags-$(CONFIG_DEBUG_DRIVER) := -DDEBUG
===================================================================
@@ -0,0 +1,946 @@
+/*
+ * drivers/base/power/runtime.c - Helper functions for device run-time PM
+ *
+ * Copyright (c) 2009 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/sched.h>
+#include <linux/pm_runtime.h>
+#include <linux/jiffies.h>
+
+static int __pm_request_resume(struct device *dev);
+
+/**
+ * pm_runtime_deactivate_timer - Deactivate given device's suspend timer.
+ * @dev: Device to handle.
+ */
+static void pm_runtime_deactivate_timer(struct device *dev)
+{
+ if (dev->power.timer_expires > 0) {
+ del_timer(&dev->power.suspend_timer);
+ dev->power.timer_expires = 0;
+ }
+}
+
+/**
+ * pm_runtime_cancel_pending - Deactivate suspend timer and cancel requests.
+ * @dev: Device to handle.
+ */
+static void pm_runtime_cancel_pending(struct device *dev)
+{
+ pm_runtime_deactivate_timer(dev);
+ /*
+ * If there's a request pending, make sure its work function will return
+ * without doing anything.
+ */
+ if (dev->power.request_pending)
+ dev->power.request = RPM_REQ_NONE;
+}
+
+/**
+ * __pm_runtime_idle - Notify device bus type if the device can be suspended.
+ * @dev: Device to notify the bus type about.
+ *
+ * This function must be called under dev->power.lock with interrupts disabled.
+ */
+static int __pm_runtime_idle(struct device *dev)
+{
+ int retval = 0;
+
+ if (dev->power.runtime_failure)
+ retval = -EINVAL;
+ else if (dev->power.idle_notification)
+ retval = -EINPROGRESS;
+ else if (atomic_read(&dev->power.usage_count) > 0
+ || dev->power.disable_depth > 0
+ || dev->power.timer_expires > 0
+ || dev->power.runtime_status == RPM_SUSPENDED
+ || dev->power.runtime_status == RPM_SUSPENDING)
+ retval = -EAGAIN;
+ else if (!pm_children_suspended(dev))
+ retval = -EBUSY;
+ if (retval)
+ return retval;
+
+ if (dev->power.request_pending) {
+ /*
+ * If an idle notification request is pending, cancel it. Any
+ * other pending request takes precedence over us.
+ */
+ if (dev->power.request == RPM_REQ_IDLE)
+ dev->power.request = RPM_REQ_NONE;
+ else if (dev->power.request != RPM_REQ_NONE)
+ return -EAGAIN;
+ }
+
+ dev->power.idle_notification = true;
+
+ spin_unlock_irq(&dev->power.lock);
+
+ if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_idle)
+ dev->bus->pm->runtime_idle(dev);
+
+ spin_lock_irq(&dev->power.lock);
+
+ dev->power.idle_notification = false;
+ wake_up_all(&dev->power.wait_queue);
+
+ return 0;
+}
+
+/**
+ * pm_runtime_idle - Notify device bus type if the device can be suspended.
+ * @dev: Device to notify the bus type about.
+ */
+int pm_runtime_idle(struct device *dev)
+{
+ int retval;
+
+ spin_lock_irq(&dev->power.lock);
+ retval = __pm_runtime_idle(dev);
+ spin_unlock_irq(&dev->power.lock);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(pm_runtime_idle);
+
+/**
+ * __pm_runtime_suspend - Carry out run-time suspend of given device.
+ * @dev: Device to suspend.
+ * @from_wq: If set, the funtion has been called via pm_wq.
+ *
+ * Check if the device can be suspended and run the ->runtime_suspend() callback
+ * provided by its bus type. If another suspend has been started earlier, wait
+ * for it to finish. If there's an idle notification pending, cancel it. If
+ * there's a suspend request scheduled while this function is running and @sync
+ * is 'true', cancel that request.
+ *
+ * This function must be called under dev->power.lock with interrupts disabled.
+ */
+int __pm_runtime_suspend(struct device *dev, bool from_wq)
+{
+ struct device *parent = NULL;
+ bool notify = false;
+ int retval = 0;
+
+ repeat:
+ if (dev->power.runtime_failure)
+ return -EINVAL;
+
+ pm_runtime_deactivate_timer(dev);
+
+ if (dev->power.request_pending) {
+ /* Pending resume requests take precedence over us. */
+ if (dev->power.request == RPM_REQ_RESUME)
+ return -EAGAIN;
+ /* Other pending requests need to be canceled. */
+ dev->power.request = RPM_REQ_NONE;
+ }
+
+ if (dev->power.runtime_status == RPM_SUSPENDED)
+ retval = 1;
+ else if (dev->power.runtime_status == RPM_RESUMING
+ || dev->power.disable_depth > 0
+ || atomic_read(&dev->power.usage_count) > 0)
+ retval = -EAGAIN;
+ else if (!pm_children_suspended(dev))
+ retval = -EBUSY;
+ if (retval)
+ return retval;
+
+ if (dev->power.runtime_status == RPM_SUSPENDING) {
+ DEFINE_WAIT(wait);
+
+ if (from_wq)
+ return -EINPROGRESS;
+
+ /* Wait for the other suspend running in parallel with us. */
+ for (;;) {
+ prepare_to_wait(&dev->power.wait_queue, &wait,
+ TASK_UNINTERRUPTIBLE);
+ if (dev->power.runtime_status != RPM_SUSPENDING)
+ break;
+
+ spin_unlock_irq(&dev->power.lock);
+
+ schedule();
+
+ spin_lock_irq(&dev->power.lock);
+ }
+ finish_wait(&dev->power.wait_queue, &wait);
+ goto repeat;
+ }
+
+ dev->power.runtime_status = RPM_SUSPENDING;
+
+ spin_unlock_irq(&dev->power.lock);
+
+ retval = dev->bus && dev->bus->pm && dev->bus->pm->runtime_suspend ?
+ dev->bus->pm->runtime_suspend(dev) : -ENOSYS;
+
+ spin_lock_irq(&dev->power.lock);
+
+ if (retval) {
+ dev->power.runtime_status = RPM_ACTIVE;
+ pm_runtime_cancel_pending(dev);
+ dev->power.deferred_resume = false;
+
+ if (retval == -EAGAIN || retval == -EBUSY) {
+ notify = true;
+ } else {
+ dev->power.runtime_failure = true;
+ dev->power.last_error = retval;
+ }
+ } else {
+ dev->power.runtime_status = RPM_SUSPENDED;
+
+ if (dev->parent) {
+ parent = dev->parent;
+ atomic_add_unless(&parent->power.child_count, -1, 0);
+ }
+
+ }
+ wake_up_all(&dev->power.wait_queue);
+
+ if (dev->power.deferred_resume) {
+ __pm_request_resume(dev);
+ dev->power.deferred_resume = false;
+ }
+
+ spin_unlock_irq(&dev->power.lock);
+
+ if (parent && !parent->power.ignore_children)
+ pm_request_idle(parent);
+
+ if (notify)
+ pm_runtime_idle(dev);
+
+ spin_lock_irq(&dev->power.lock);
+
+ return retval;
+}
+
+/**
+ * pm_runtime_suspend - Carry out run-time suspend of given device.
+ * @dev: Device to suspend.
+ */
+int pm_runtime_suspend(struct device *dev)
+{
+ int retval;
+
+ spin_lock_irq(&dev->power.lock);
+ retval = __pm_runtime_suspend(dev, false);
+ spin_unlock_irq(&dev->power.lock);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(pm_runtime_suspend);
+
+/**
+ * __pm_runtime_resume - Carry out run-time resume of given device.
+ * @dev: Device to resume.
+ * @from_wq: If set, the funtion has been called via pm_wq.
+ *
+ * Check if the device can be woken up and run the ->runtime_resume() callback
+ * provided by its bus type. If another resume has been started earlier, wait
+ * for it to finish. If there's a suspend running in parallel with this
+ * function, wait for it to finish and resume the device. If there's a suspend
+ * request or idle notification pending, cancel it. If there's a resume request
+ * scheduled while this function is running, cancel that request.
+ *
+ * This function must be called under dev->power.lock with interrupts disabled.
+ */
+int __pm_runtime_resume(struct device *dev, bool from_wq)
+{
+ struct device *parent = NULL;
+ int retval = 0;
+
+ repeat:
+ if (dev->power.runtime_failure)
+ return -EINVAL;
+
+ pm_runtime_cancel_pending(dev);
+
+ if (dev->power.runtime_status == RPM_ACTIVE)
+ retval = 1;
+ else if (dev->power.disable_depth > 0)
+ retval = -EAGAIN;
+ if (retval)
+ return retval;
+
+ if (dev->power.runtime_status == RPM_RESUMING
+ || dev->power.runtime_status == RPM_SUSPENDING) {
+ DEFINE_WAIT(wait);
+
+ if (from_wq) {
+ if (dev->power.runtime_status == RPM_SUSPENDING)
+ dev->power.deferred_resume = true;
+ return -EINPROGRESS;
+ }
+
+ /* Wait for the operation carried out in parallel with us. */
+ for (;;) {
+ prepare_to_wait(&dev->power.wait_queue, &wait,
+ TASK_UNINTERRUPTIBLE);
+ if (dev->power.runtime_status != RPM_RESUMING
+ && dev->power.runtime_status != RPM_SUSPENDING)
+ break;
+
+ spin_unlock_irq(&dev->power.lock);
+
+ schedule();
+
+ spin_lock_irq(&dev->power.lock);
+ }
+ finish_wait(&dev->power.wait_queue, &wait);
+ goto repeat;
+ }
+
+ if (!parent && dev->parent) {
+ /*
+ * Increment the parent's resume counter and resume it if
+ * necessary.
+ */
+ spin_unlock_irq(&dev->power.lock);
+
+ parent = dev->parent;
+ retval = pm_runtime_get_sync(parent);
+ if (retval < 0)
+ goto out_parent;
+
+ spin_lock_irq(&dev->power.lock);
+ retval = 0;
+ goto repeat;
+ }
+
+ dev->power.runtime_status = RPM_RESUMING;
+
+ spin_unlock_irq(&dev->power.lock);
+
+ retval = dev->bus && dev->bus->pm && dev->bus->pm->runtime_resume ?
+ dev->bus->pm->runtime_resume(dev) : -ENOSYS;
+
+ spin_lock_irq(&dev->power.lock);
+
+ if (retval) {
+ dev->power.runtime_status = RPM_SUSPENDED;
+
+ dev->power.runtime_failure = true;
+ dev->power.last_error = retval;
+
+ pm_runtime_cancel_pending(dev);
+ } else {
+ dev->power.runtime_status = RPM_ACTIVE;
+
+ if (parent)
+ atomic_inc(&parent->power.child_count);
+ }
+ wake_up_all(&dev->power.wait_queue);
+
+ spin_unlock_irq(&dev->power.lock);
+
+ out_parent:
+ if (parent)
+ pm_runtime_put(parent);
+
+ if (!retval)
+ pm_request_idle(dev);
+
+ spin_lock_irq(&dev->power.lock);
+
+ return retval;
+}
+
+/**
+ * pm_runtime_resume - Carry out run-time resume of given device.
+ * @dev: Device to suspend.
+ */
+int pm_runtime_resume(struct device *dev)
+{
+ int retval;
+
+ spin_lock_irq(&dev->power.lock);
+ retval = __pm_runtime_resume(dev, false);
+ spin_unlock_irq(&dev->power.lock);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(pm_runtime_resume);
+
+/**
+ * pm_runtime_work - Universal run-time PM work function.
+ * @work: Work structure used for scheduling the execution of this function.
+ *
+ * Use @work to get the device object the work is to be done for, determine what
+ * is to be done and execute the appropriate run-time PM function.
+ */
+static void pm_runtime_work(struct work_struct *work)
+{
+ struct device *dev = container_of(work, struct device, power.work);
+ enum rpm_request req;
+
+ spin_lock_irq(&dev->power.lock);
+
+ if (!dev->power.request_pending)
+ goto out;
+
+ req = dev->power.request;
+ dev->power.request = RPM_REQ_NONE;
+ dev->power.request_pending = false;
+
+ switch (req) {
+ case RPM_REQ_NONE:
+ break;
+ case RPM_REQ_IDLE:
+ __pm_runtime_idle(dev);
+ break;
+ case RPM_REQ_SUSPEND:
+ __pm_runtime_suspend(dev, true);
+ break;
+ case RPM_REQ_RESUME:
+ __pm_runtime_resume(dev, true);
+ break;
+ }
+
+ out:
+ spin_unlock_irq(&dev->power.lock);
+}
+
+/**
+ * pm_request_idle - Submit an idle notification request for given device.
+ * @dev: Device to handle.
+ *
+ * Check if the device's run-time PM status is correct for suspending the device
+ * and queue up a request to run __pm_runtime_idle() for it.
+ */
+int pm_request_idle(struct device *dev)
+{
+ unsigned long flags;
+ int retval = 0;
+
+ spin_lock_irqsave(&dev->power.lock, flags);
+
+ if (dev->power.runtime_failure)
+ retval = -EINVAL;
+ else if (atomic_read(&dev->power.usage_count) > 0
+ || dev->power.disable_depth > 0
+ || dev->power.timer_expires > 0
+ || dev->power.runtime_status == RPM_SUSPENDED
+ || dev->power.runtime_status == RPM_SUSPENDING)
+ retval = -EAGAIN;
+ else if (!pm_children_suspended(dev))
+ retval = -EBUSY;
+ if (retval)
+ goto out;
+
+ if (dev->power.request_pending && dev->power.request != RPM_REQ_NONE) {
+ /* Any requests other then RPM_REQ_IDLE take precedence. */
+ if (dev->power.request != RPM_REQ_IDLE)
+ retval = -EAGAIN;
+ goto out;
+ }
+
+ dev->power.request = RPM_REQ_IDLE;
+ if (dev->power.request_pending)
+ goto out;
+
+ dev->power.request_pending = true;
+ queue_work(pm_wq, &dev->power.work);
+
+ out:
+ spin_unlock_irqrestore(&dev->power.lock, flags);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(pm_request_idle);
+
+/**
+ * __pm_request_suspend - Submit a suspend request for given device.
+ * @dev: Device to suspend.
+ *
+ * This function must be called under dev->power.lock with interrupts disabled.
+ */
+static int __pm_request_suspend(struct device *dev)
+{
+ int retval = 0;
+
+ if (dev->power.runtime_failure)
+ return -EINVAL;
+
+ if (dev->power.runtime_status == RPM_SUSPENDED)
+ retval = 1;
+ else if (atomic_read(&dev->power.usage_count) > 0
+ || dev->power.disable_depth > 0)
+ retval = -EAGAIN;
+ else if (dev->power.runtime_status == RPM_SUSPENDING)
+ retval = -EINPROGRESS;
+ else if (!pm_children_suspended(dev))
+ retval = -EBUSY;
+
+ pm_runtime_deactivate_timer(dev);
+
+ if (dev->power.request_pending) {
+ /*
+ * Pending resume requests take precedence over us, but we can
+ * overtake any other pending request.
+ */
+ if (dev->power.request == RPM_REQ_RESUME)
+ retval = -EAGAIN;
+ else if (dev->power.request != RPM_REQ_SUSPEND)
+ dev->power.request = retval ?
+ RPM_REQ_NONE : RPM_REQ_SUSPEND;
+
+ if (dev->power.request == RPM_REQ_SUSPEND)
+ return 0;
+ }
+
+ if (retval)
+ return retval;
+
+ dev->power.request = RPM_REQ_SUSPEND;
+ dev->power.request_pending = true;
+ queue_work(pm_wq, &dev->power.work);
+
+ return 0;
+}
+
+/**
+ * pm_suspend_timer_fn - Timer function for pm_schedule_suspend().
+ * @data: Device pointer passed by pm_schedule_suspend().
+ *
+ * Check if the time is right and execute __pm_request_suspend() in that case.
+ */
+static void pm_suspend_timer_fn(unsigned long data)
+{
+ struct device *dev = (struct device *)data;
+ unsigned long flags;
+ unsigned long expires;
+
+ spin_lock_irqsave(&dev->power.lock, flags);
+
+ expires = dev->power.timer_expires;
+ /* If 'expire' is after 'jiffies' we've been called too early. */
+ if (expires > 0 && !time_after(expires, jiffies)) {
+ dev->power.timer_expires = 0;
+ __pm_request_suspend(dev);
+ }
+
+ spin_unlock_irqrestore(&dev->power.lock, flags);
+}
+
+/**
+ * pm_schedule_suspend - Set up a timer to submit a suspend request in future.
+ * @dev: Device to suspend.
+ * @delay: Time to wait before submitting a suspend request, in milliseconds.
+ */
+int pm_schedule_suspend(struct device *dev, unsigned int delay)
+{
+ unsigned long flags;
+ int retval = 0;
+
+ spin_lock_irqsave(&dev->power.lock, flags);
+
+ if (dev->power.runtime_failure) {
+ retval = -EINVAL;
+ goto out;
+ }
+
+ if (!delay) {
+ retval = __pm_request_suspend(dev);
+ goto out;
+ }
+
+ pm_runtime_deactivate_timer(dev);
+
+ if (dev->power.request_pending) {
+ /*
+ * Pending resume requests take precedence over us, but any
+ * other pending requests have to be canceled.
+ */
+ if (dev->power.request == RPM_REQ_RESUME) {
+ retval = -EAGAIN;
+ goto out;
+ }
+ dev->power.request = RPM_REQ_NONE;
+ }
+
+ if (dev->power.runtime_status == RPM_SUSPENDED)
+ retval = 1;
+ else if (dev->power.runtime_status == RPM_SUSPENDING)
+ retval = -EINPROGRESS;
+ else if (atomic_read(&dev->power.usage_count) > 0
+ || dev->power.disable_depth > 0)
+ retval = -EAGAIN;
+ else if (!pm_children_suspended(dev))
+ retval = -EBUSY;
+ if (retval)
+ goto out;
+
+ dev->power.timer_expires = jiffies + msecs_to_jiffies(delay);
+ mod_timer(&dev->power.suspend_timer, dev->power.timer_expires);
+
+ out:
+ spin_unlock_irqrestore(&dev->power.lock, flags);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(pm_schedule_suspend);
+
+/**
+ * pm_request_resume - Submit a resume request for given device.
+ * @dev: Device to resume.
+ *
+ * This function must be called under dev->power.lock with interrupts disabled.
+ */
+int __pm_request_resume(struct device *dev)
+{
+ int retval = 0;
+
+ if (dev->power.runtime_failure)
+ return -EINVAL;
+
+ if (dev->power.runtime_status == RPM_ACTIVE)
+ retval = 1;
+ else if (dev->power.runtime_status == RPM_RESUMING)
+ retval = -EINPROGRESS;
+ else if (dev->power.disable_depth > 0)
+ retval = -EAGAIN;
+
+ pm_runtime_deactivate_timer(dev);
+
+ if (dev->power.request_pending) {
+ /* If non-resume request is pending, we can overtake it. */
+ dev->power.request = retval ? RPM_REQ_NONE : RPM_REQ_RESUME;
+ /* There's nothing to do if resume request is pending. */
+ if (dev->power.request == RPM_REQ_RESUME)
+ return 0;
+ }
+
+ if (retval)
+ return retval;
+
+ dev->power.request = RPM_REQ_RESUME;
+ dev->power.request_pending = true;
+ queue_work(pm_wq, &dev->power.work);
+
+ return retval;
+}
+
+/**
+ * pm_request_resume - Submit a resume request for given device.
+ * @dev: Device to resume.
+ */
+int pm_request_resume(struct device *dev)
+{
+ unsigned long flags;
+ int retval;
+
+ spin_lock_irqsave(&dev->power.lock, flags);
+ retval = __pm_request_resume(dev);
+ spin_unlock_irqrestore(&dev->power.lock, flags);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(pm_request_resume);
+
+/**
+ * __pm_runtime_get - Reference count a device and wake it up, if necessary.
+ * @dev: Device to handle.
+ * @sync: If set and the device is suspended, resume it synchronously.
+ *
+ * Increment the usage count of the device and if it was zero previously,
+ * resume it or submit a resume request for it, depending on the value of @sync.
+ */
+int __pm_runtime_get(struct device *dev, bool sync)
+{
+ int retval = 1;
+
+ if (atomic_add_return(1, &dev->power.usage_count) == 1)
+ retval = sync ? pm_runtime_resume(dev) : pm_request_resume(dev);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(__pm_runtime_get);
+
+/**
+ * __pm_runtime_put - Decrement the device's usage counter and notify its bus.
+ * @dev: Device to handle.
+ * @sync: If the device's bus type is to be notified, do that synchronously.
+ *
+ * Decrement the usage count of the device and if it reaches zero, carry out a
+ * synchronous idle notification or submit an idle notification request for it,
+ * depending on the value of @sync.
+ */
+int __pm_runtime_put(struct device *dev, bool sync)
+{
+ int retval = 0;
+
+ if (atomic_dec_and_test(&dev->power.usage_count))
+ retval = sync ? pm_runtime_idle(dev) : pm_request_idle(dev);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(__pm_runtime_put);
+
+/**
+ * __pm_runtime_set_status - Set run-time PM status of a device.
+ * @dev: Device to handle.
+ * @status: New run-time PM status of the device.
+ *
+ * If run-time PM of the device is disabled or its power.runtime_failure flag is
+ * set, the status may be changed either to RPM_ACTIVE, or to RPM_SUSPENDED, as
+ * long as that reflects the actual state of the device. However, if the device
+ * has a parent and the parent is not active, and the parent's
+ * power.ignore_children flag is unset, the device's status cannot be set to
+ * RPM_ACTIVE, so -EBUSY is returned in that case.
+ *
+ * If successful, __pm_runtime_set_status() clears the power.runtime_failure
+ * flag and the device parent's counter of unsuspended children is modified to
+ * reflect the new status.
+ */
+int __pm_runtime_set_status(struct device *dev, unsigned int status)
+{
+ struct device *parent = dev->parent;
+ unsigned long flags;
+ int error = 0;
+
+ if (status != RPM_ACTIVE && status != RPM_SUSPENDED)
+ return -EINVAL;
+
+ spin_lock_irqsave(&dev->power.lock, flags);
+
+ if (!dev->power.runtime_failure && !dev->power.disable_depth)
+ goto out;
+
+ if (dev->power.runtime_status == status)
+ goto out_clear;
+
+ if (status == RPM_SUSPENDED) {
+ /* It always is possible to set the status to 'suspended'. */
+ if (parent)
+ atomic_add_unless(&parent->power.child_count, -1, 0);
+ dev->power.runtime_status = status;
+ goto out_clear;
+ }
+
+ if (parent) {
+ spin_lock_irq(&parent->power.lock);
+
+ /*
+ * It is invalid to put an active child under a parent that is
+ * not active, has run-time PM enabled and the
+ * 'power.ignore_children' flag unset.
+ */
+ if (!parent->power.disable_depth
+ && !parent->power.ignore_children
+ && parent->power.runtime_status != RPM_ACTIVE) {
+ error = -EBUSY;
+ } else {
+ if (dev->power.runtime_status == RPM_SUSPENDED)
+ atomic_inc(&parent->power.child_count);
+ dev->power.runtime_status = status;
+ }
+
+ spin_unlock_irq(&parent->power.lock);
+
+ if (error)
+ goto out;
+ } else {
+ dev->power.runtime_status = status;
+ }
+
+ out_clear:
+ dev->power.runtime_failure = false;
+ out:
+ spin_unlock_irqrestore(&dev->power.lock, flags);
+
+ return error;
+}
+EXPORT_SYMBOL_GPL(__pm_runtime_set_status);
+
+/**
+ * pm_runtime_enable - Enable run-time PM of a device.
+ * @dev: Device to handle.
+ */
+void pm_runtime_enable(struct device *dev)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&dev->power.lock, flags);
+
+ if (dev->power.disable_depth > 0)
+ dev->power.disable_depth--;
+ else
+ dev_warn(dev, "Unbalanced %s!", __func__);
+
+ spin_unlock_irqrestore(&dev->power.lock, flags);
+}
+EXPORT_SYMBOL_GPL(pm_runtime_enable);
+
+/**
+ * pm_runtime_disable - Disable run-time PM of a device.
+ * @dev: Device to handle.
+ *
+ * Increment power.disable_depth for the device and if was zero previously,
+ * cancel all pending run-time PM requests for the device and wait for all
+ * operations in progress to complete. The device can be either active or
+ * suspended after its run-time PM has been disabled.
+ *
+ * If there's a resume request pending when pm_runtime_disable() is called and
+ * power.disable_depth is zero, the function will wake up the device before
+ * disabling its run-time PM and will return 1. Otherwise, 0 is returned.
+ */
+int pm_runtime_disable(struct device *dev)
+{
+ int retval = 0;
+
+ spin_lock_irq(&dev->power.lock);
+
+ if (dev->power.disable_depth > 0) {
+ dev->power.disable_depth++;
+ goto out;
+ }
+
+ /*
+ * Wake up the device if there's a resume request pending, because that
+ * means there probably is some I/O to process and disabling run-time PM
+ * shouldn't prevent the device from processing the I/O.
+ */
+ if (dev->power.request_pending
+ && dev->power.request == RPM_REQ_RESUME) {
+ /*
+ * Prevent suspends and idle notifications from being carried
+ * out after we have woken up the device.
+ */
+ pm_runtime_get_noresume(dev);
+
+ __pm_runtime_resume(dev, false);
+
+ pm_runtime_put_noidle(dev);
+ retval = 1;
+ }
+
+ if (dev->power.disable_depth++ > 0)
+ goto out;
+
+ if (dev->power.runtime_failure)
+ goto out;
+
+ pm_runtime_deactivate_timer(dev);
+
+ if (dev->power.request_pending) {
+ dev->power.request = RPM_REQ_NONE;
+
+ spin_unlock_irq(&dev->power.lock);
+
+ cancel_work_sync(&dev->power.work);
+
+ spin_lock_irq(&dev->power.lock);
+
+ dev->power.request_pending = false;
+ }
+
+ if (dev->power.runtime_status == RPM_SUSPENDING
+ || dev->power.runtime_status == RPM_RESUMING) {
+ DEFINE_WAIT(wait);
+
+ /* Suspend or wake-up in progress. */
+ for (;;) {
+ prepare_to_wait(&dev->power.wait_queue, &wait,
+ TASK_UNINTERRUPTIBLE);
+ if (dev->power.runtime_status != RPM_SUSPENDING
+ && dev->power.runtime_status != RPM_RESUMING)
+ break;
+
+ spin_unlock_irq(&dev->power.lock);
+
+ schedule();
+
+ spin_lock_irq(&dev->power.lock);
+ }
+ finish_wait(&dev->power.wait_queue, &wait);
+ }
+
+ if (dev->power.runtime_failure)
+ goto out;
+
+ if (dev->power.idle_notification) {
+ DEFINE_WAIT(wait);
+
+ for (;;) {
+ prepare_to_wait(&dev->power.wait_queue, &wait,
+ TASK_UNINTERRUPTIBLE);
+ if (!dev->power.idle_notification)
+ break;
+
+ spin_unlock_irq(&dev->power.lock);
+
+ schedule();
+
+ spin_lock_irq(&dev->power.lock);
+ }
+ finish_wait(&dev->power.wait_queue, &wait);
+ }
+
+ out:
+ spin_unlock_irq(&dev->power.lock);
+
+ return retval;
+}
+EXPORT_SYMBOL_GPL(pm_runtime_disable);
+
+/**
+ * pm_runtime_init - Initialize run-time PM fields in given device object.
+ * @dev: Device object to initialize.
+ */
+void pm_runtime_init(struct device *dev)
+{
+ spin_lock_init(&dev->power.lock);
+
+ dev->power.runtime_status = RPM_SUSPENDED;
+ dev->power.idle_notification = false;
+
+ dev->power.disable_depth = 1;
+ atomic_set(&dev->power.usage_count, 0);
+
+ dev->power.runtime_failure = false;
+ dev->power.last_error = 0;
+
+ atomic_set(&dev->power.child_count, 0);
+ pm_suspend_ignore_children(dev, false);
+
+ dev->power.request_pending = false;
+ dev->power.request = RPM_REQ_NONE;
+ dev->power.deferred_resume = false;
+ INIT_WORK(&dev->power.work, pm_runtime_work);
+
+ dev->power.timer_expires = 0;
+ dev->power.suspend_timer.expires = jiffies;
+ dev->power.suspend_timer.data = (unsigned long)dev;
+ dev->power.suspend_timer.function = pm_suspend_timer_fn;
+
+ init_waitqueue_head(&dev->power.wait_queue);
+}
+
+/**
+ * pm_runtime_remove - Prepare for removing a device from device hierarchy.
+ * @dev: Device object being removed from device hierarchy.
+ */
+void pm_runtime_remove(struct device *dev)
+{
+ pm_runtime_disable(dev);
+
+ if (dev->power.runtime_status == RPM_ACTIVE) {
+ struct device *parent = dev->parent;
+
+ /*
+ * Change the status back to 'suspended' to match the initial
+ * status.
+ */
+ pm_runtime_set_suspended(dev);
+ if (parent && !parent->power.ignore_children)
+ pm_request_idle(parent);
+ }
+}
===================================================================
@@ -0,0 +1,111 @@
+/*
+ * pm_runtime.h - Device run-time power management helper functions.
+ *
+ * Copyright (C) 2009 Rafael J. Wysocki <rjw@sisk.pl>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#ifndef _LINUX_PM_RUNTIME_H
+#define _LINUX_PM_RUNTIME_H
+
+#include <linux/device.h>
+#include <linux/pm.h>
+
+#ifdef CONFIG_PM_RUNTIME
+
+extern struct workqueue_struct *pm_wq;
+
+extern void pm_runtime_init(struct device *dev);
+extern void pm_runtime_remove(struct device *dev);
+extern int pm_runtime_idle(struct device *dev);
+extern int pm_runtime_suspend(struct device *dev);
+extern int pm_runtime_resume(struct device *dev);
+extern int pm_request_idle(struct device *dev);
+extern int pm_schedule_suspend(struct device *dev, unsigned int delay);
+extern int pm_request_resume(struct device *dev);
+extern int __pm_runtime_get(struct device *dev, bool sync);
+extern int __pm_runtime_put(struct device *dev, bool sync);
+extern int __pm_runtime_set_status(struct device *dev, unsigned int status);
+extern void pm_runtime_enable(struct device *dev);
+extern int pm_runtime_disable(struct device *dev);
+
+static inline bool pm_children_suspended(struct device *dev)
+{
+ return dev->power.ignore_children
+ || !atomic_read(&dev->power.child_count);
+}
+
+static inline void pm_suspend_ignore_children(struct device *dev, bool enable)
+{
+ dev->power.ignore_children = enable;
+}
+
+static inline void pm_runtime_get_noresume(struct device *dev)
+{
+ atomic_inc(&dev->power.usage_count);
+}
+
+static inline void pm_runtime_put_noidle(struct device *dev)
+{
+ atomic_add_unless(&dev->power.usage_count, -1, 0);
+}
+
+#else /* !CONFIG_PM_RUNTIME */
+
+static inline void pm_runtime_init(struct device *dev) {}
+static inline void pm_runtime_remove(struct device *dev) {}
+static inline int pm_runtime_idle(struct device *dev) { return -ENOSYS; }
+static inline int pm_runtime_suspend(struct device *dev) { return -ENOSYS; }
+static inline int pm_runtime_resume(struct device *dev) { return 0; }
+static inline int pm_request_idle(struct device *dev) { return -ENOSYS; }
+static inline int pm_schedule_suspend(struct device *dev, unsigned int delay)
+{
+ return -ENOSYS;
+}
+static inline int pm_request_resume(struct device *dev) { return 0; }
+static inline int __pm_runtime_get(struct device *dev, bool sync) { return 1; }
+static inline int __pm_runtime_put(struct device *dev, bool sync) { return 0; }
+static inline int __pm_runtime_set_status(struct device *dev,
+ unsigned int status) { return 0; }
+static inline void pm_runtime_enable(struct device *dev) {}
+static inline int pm_runtime_disable(struct device *dev) { return 0; }
+
+static inline bool pm_children_suspended(struct device *dev) { return false; }
+static inline void pm_suspend_ignore_children(struct device *dev, bool en) {}
+static inline void pm_runtime_get_noresume(struct device *dev) {}
+static inline void pm_runtime_put_noidle(struct device *dev) {}
+
+#endif /* !CONFIG_PM_RUNTIME */
+
+static inline int pm_runtime_get(struct device *dev)
+{
+ return __pm_runtime_get(dev, false);
+}
+
+static inline int pm_runtime_get_sync(struct device *dev)
+{
+ return __pm_runtime_get(dev, true);
+}
+
+static inline int pm_runtime_put(struct device *dev)
+{
+ return __pm_runtime_put(dev, false);
+}
+
+static inline int pm_runtime_put_sync(struct device *dev)
+{
+ return __pm_runtime_put(dev, true);
+}
+
+static inline int pm_runtime_set_active(struct device *dev)
+{
+ return __pm_runtime_set_status(dev, RPM_ACTIVE);
+}
+
+static inline void pm_runtime_set_suspended(struct device *dev)
+{
+ __pm_runtime_set_status(dev, RPM_SUSPENDED);
+}
+
+#endif
===================================================================
@@ -21,6 +21,7 @@
#include <linux/kallsyms.h>
#include <linux/mutex.h>
#include <linux/pm.h>
+#include <linux/pm_runtime.h>
#include <linux/resume-trace.h>
#include <linux/rwsem.h>
#include <linux/interrupt.h>
@@ -49,6 +50,16 @@ static DEFINE_MUTEX(dpm_list_mtx);
static bool transition_started;
/**
+ * device_pm_init - Initialize the PM-related part of a device object
+ * @dev: Device object to initialize.
+ */
+void device_pm_init(struct device *dev)
+{
+ dev->power.status = DPM_ON;
+ pm_runtime_init(dev);
+}
+
+/**
* device_pm_lock - lock the list of active devices used by the PM core
*/
void device_pm_lock(void)
@@ -105,6 +116,8 @@ void device_pm_remove(struct device *dev
mutex_lock(&dpm_list_mtx);
list_del_init(&dev->power.entry);
mutex_unlock(&dpm_list_mtx);
+
+ pm_runtime_remove(dev);
}
/**
@@ -512,6 +525,7 @@ static void dpm_complete(pm_message_t st
mutex_unlock(&dpm_list_mtx);
device_complete(dev, state);
+ pm_runtime_enable(dev);
mutex_lock(&dpm_list_mtx);
}
@@ -757,11 +771,15 @@ static int dpm_prepare(pm_message_t stat
dev->power.status = DPM_PREPARING;
mutex_unlock(&dpm_list_mtx);
- error = device_prepare(dev, state);
+ if (pm_runtime_disable(dev) && device_may_wakeup(dev))
+ error = -EBUSY;
+ else
+ error = device_prepare(dev, state);
mutex_lock(&dpm_list_mtx);
if (error) {
dev->power.status = DPM_ON;
+ pm_runtime_enable(dev);
if (error == -EAGAIN) {
put_device(dev);
error = 0;
===================================================================
@@ -23,6 +23,7 @@
#include <linux/kthread.h>
#include <linux/wait.h>
#include <linux/async.h>
+#include <linux/pm_runtime.h>
#include "base.h"
#include "power/power.h"
@@ -202,7 +203,9 @@ int driver_probe_device(struct device_dr
pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
drv->bus->name, __func__, dev_name(dev), drv->name);
+ pm_runtime_get_noresume(dev);
ret = really_probe(dev, drv);
+ pm_runtime_put_noidle(dev);
return ret;
}
@@ -306,6 +309,8 @@ static void __device_release_driver(stru
drv = dev->driver;
if (drv) {
+ pm_runtime_disable(dev);
+
driver_sysfs_remove(dev);
if (dev->bus)
@@ -324,6 +329,8 @@ static void __device_release_driver(stru
blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
BUS_NOTIFY_UNBOUND_DRIVER,
dev);
+
+ pm_runtime_enable(dev);
}
}
===================================================================
@@ -1,8 +1,3 @@
-static inline void device_pm_init(struct device *dev)
-{
- dev->power.status = DPM_ON;
-}
-
#ifdef CONFIG_PM_SLEEP
/*
@@ -16,14 +11,16 @@ static inline struct device *to_device(s
return container_of(entry, struct device, power.entry);
}
+extern void device_pm_init(struct device *dev);
extern void device_pm_add(struct device *);
extern void device_pm_remove(struct device *);
extern void device_pm_move_before(struct device *, struct device *);
extern void device_pm_move_after(struct device *, struct device *);
extern void device_pm_move_last(struct device *);
-#else /* CONFIG_PM_SLEEP */
+#else /* !CONFIG_PM_SLEEP */
+static inline void device_pm_init(struct device *dev) {}
static inline void device_pm_add(struct device *dev) {}
static inline void device_pm_remove(struct device *dev) {}
static inline void device_pm_move_before(struct device *deva,
@@ -32,7 +29,7 @@ static inline void device_pm_move_after(
struct device *devb) {}
static inline void device_pm_move_last(struct device *dev) {}
-#endif
+#endif /* !CONFIG_PM_SLEEP */
#ifdef CONFIG_PM
===================================================================
@@ -0,0 +1,340 @@
+Run-time Power Management Framework for I/O Devices
+
+(C) 2009 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
+
+1. Introduction
+
+Support for run-time power management (run-time PM) of I/O devices is provided
+at the power management core (PM core) level by means of:
+
+* The power management workqueue pm_wq in which bus types and device drivers can
+ put their PM-related work items. It is strongly recommended that pm_wq be
+ used for queuing all work items related to run-time PM, because this allows
+ them to be synchronized with system-wide power transitions (suspend to RAM,
+ hibernation and resume from system sleep states). pm_wq is declared in
+ include/linux/pm_runtime.h and defined in kernel/power/main.c.
+
+* A number of run-time PM fields in the 'power' member of 'struct device' (which
+ is of the type 'struct dev_pm_info', defined in include/linux/pm.h) that can
+ be used for synchronizing run-time PM operations with one another.
+
+* Three device run-time PM callbacks in 'struct dev_pm_ops' (defined in
+ include/linux/pm.h).
+
+* A set of helper functions defined in drivers/base/power/runtime.c that can be
+ used for carrying out run-time PM operations in such a way that the
+ synchronization between them is taken care of by the PM core. Bus types and
+ device drivers are encouraged to use these functions.
+
+The run-time PM callbacks present in 'struct dev_pm_ops', the device run-time PM
+fields of 'struct dev_pm_info' and the core helper functions provided for
+run-time PM are described below.
+
+2. Device Run-time PM Callbacks
+
+There are three device run-time PM callbacks defined in 'struct dev_pm_ops':
+
+struct dev_pm_ops {
+ ...
+ int (*runtime_suspend)(struct device *dev);
+ int (*runtime_resume)(struct device *dev);
+ void (*runtime_idle)(struct device *dev);
+ ...
+};
+
+The ->runtime_suspend() callback is executed by the PM core for the bus type of
+the device being suspended. The bus type's callback is then _entirely_
+_responsible_ for handling the device as appropriate, which may, but need not
+include executing the device driver's own ->runtime_suspend() callback (from the
+PM core's point of view it is not necessary to implement a ->runtime_suspend()
+callback in a device driver as long as the bus type's ->runtime_suspend() knows
+what to do to handle the device).
+
+ * Once the bus type's ->runtime_suspend() callback has completed successfully
+ for given device, the PM core regards the device as suspended, which need
+ not mean that the device has been put into a low power state. It is
+ supposed to mean, however, that the device will not process data and will
+ not communicate with the CPU(s) and RAM until its bus type's
+ ->runtime_resume() callback is executed for it. The run-time PM status of
+ a device after successful execution of its bus type's ->runtime_suspend()
+ callback is 'suspended'.
+
+ * If the bus type's ->runtime_suspend() callback returns -EBUSY or -EAGAIN,
+ the device's run-time PM status is supposed to be 'active', which means that
+ the device _must_ be fully operational afterwards.
+
+ * If the bus type's ->runtime_suspend() callback returns an error code
+ different from -EBUSY or -EAGAIN, the PM core regards this as a fatal
+ error and will refuse to run the helper functions described in Section 4
+ for the device, until the status of it is directly set either to 'active'
+ or to 'suspended' (the PM core provides special helper functions for this
+ purpose).
+
+In particular, it is recommended that ->runtime_suspend() return -EBUSY if
+device_may_wakeup() returns 'false' for the device. On the other hand, if
+device_may_wakeup() returns 'true' for the device and the device is put
+into a low power state during the execution of its bus type's
+->runtime_suspend(), it is expected that remote wake-up (i.e. hardware mechanism
+allowing the device to request a change of its power state, such as PCI PME)
+will be enabled for the device. Generally, remote wake-up should be enabled
+for all input devices put into a low power state at run time.
+
+The ->runtime_resume() callback is executed by the PM core for the bus type of
+the device being woken up. The bus type's callback is then _entirely_
+_responsible_ for handling the device as appropriate, which may, but need not
+include executing the device driver's own ->runtime_resume() callback (from the
+PM core's point of view it is not necessary to implement a ->runtime_resume()
+callback in a device driver as long as the bus type's ->runtime_resume() knows
+what to do to handle the device).
+
+ * Once the bus type's ->runtime_resume() callback has completed successfully,
+ the PM core regards the device as fully operational, which means that the
+ device _must_ be able to complete I/O operations as needed. The run-time
+ PM status of the device is then 'active'.
+
+ * If the bus type's ->runtime_resume() callback returns an error code, the PM
+ core regards this as a fatal error and will refuse to run the helper
+ functions described in Section 4 for the device, until its status is
+ directly set either to 'active' or to 'suspended' (the PM core provides
+ special helper functions for this purpose).
+
+The ->runtime_idle() callback is executed by the PM core for the bus type of
+given device whenever the device appears to be idle, which is indicated to the
+PM core by two counters, the device's usage counter and the counter of 'active'
+children of the device.
+
+ * If any of these counters is decreased using a helper function provided by
+ the PM core and it turns out to be equal to zero, the other counter is
+ checked. If that counter also is equal to zero, the PM core executes the
+ device bus type's ->runtime_idle() callback (with the device as an
+ argument).
+
+The action performed by a bus type's ->runtime_idle() callback is totally
+dependent on the bus type in question, but the expected and recommended action
+is to check if the device can be suspended (i.e. if all of the conditions
+necessary for suspending the device are satisfied) and to queue up a suspend
+request for the device in that case.
+
+The helper functions provided by the PM core, described in Section 4, guarantee
+that the following constraints are met with respect to the bus type's run-time
+PM callbacks:
+
+(1) The callbacks are mutually exclusive (e.g. it is forbidden to execute
+ ->runtime_suspend() in parallel with ->runtime_resume() or with another
+ instance of ->runtime_suspend() for the same device) with the exception that
+ ->runtime_suspend() or ->runtime_resume() can be executed in parallel with
+ ->runtime_idle() (although ->runtime_idle() will not be started while any
+ of the other callbacks is being executed for the same device).
+
+(2) ->runtime_idle() and ->runtime_suspend() can only be executed for 'active'
+ devices (i.e. the PM core will only execute ->runtime_idle() or
+ ->runtime_suspend() for the devices the run-time PM status of which is
+ 'active').
+
+(3) ->runtime_idle() and ->runtime_suspend() can only be executed for a device
+ the usage counter of which is equal to zero _and_ either the counter of
+ 'active' children of which is equal to zero, or the 'power.ignore_children'
+ flag of which is set.
+
+(4) ->runtime_resume() can only be executed for 'suspended' devices (i.e. the
+ PM core will only execute ->runtime_resume() for the devices the run-time
+ PM status of which is 'suspended').
+
+Additionally, the helper functions provided by the PM core obey the following
+rules:
+
+ * If ->runtime_suspend() is about to be executed or the execution of it is
+ scheduled or there's a pending request to execute it, ->runtime_idle() will
+ not be executed for the same device.
+
+ * A request to execute or to schedule the execution of ->runtime_suspend()
+ will cancel any pending requests to execute ->runtime_idle() for the same
+ device.
+
+ * If ->runtime_resume() is about to be executed or there's a pending request
+ to execute it, the other callbacks will not be executed for the same device.
+
+ * A request to execute ->runtime_resume() will cancel any pending or
+ scheduled requests to execute the other callbacks for the same device.
+
+3. Run-time PM Device Fields
+
+The following device run-time PM fields are present in 'struct dev_pm_info', as
+defined in include/linux/pm.h:
+
+ struct timer_list suspend_timer;
+ - timer used for scheduling (delayed) suspend request
+
+ unsigned long timer_expires;
+ - timer expiration time, in jiffies (if this is different from zero, the
+ timer is running and will expire at that time, otherwise the timer is not
+ running)
+
+ struct work_struct work;
+ - work structure used for queuing up requests (i.e. work items in pm_wq)
+
+ wait_queue_head_t wait_queue;
+ - wait queue used if any of the helper functions needs to wait for another
+ one to complete
+
+ spinlock_t lock;
+ - lock used for synchronisation
+
+ atomic_t usage_count;
+ - the usage counter of the device
+
+ atomic_t child_count;
+ - the count of 'active' children of the device
+
+ unsigned int ignore_children;
+ - if set, the value of child_count is ignored (but still updated)
+
+ unsigned int disable_depth;
+ - used for disabling the helper funcions (they work normally if this is
+ equal to zero); the initial value of it is 1 (i.e. run-time PM is
+ initially disabled for all devices)
+
+ unsigned int runtime_failure;
+ - if set, there was a fatal error (one of the callbacks returned error code
+ as described in Section 2), so the helper funtions will not work until
+ this flag is cleared
+
+ int last_error;
+ - if runtime_failure is set, this is the error code returned by the
+ failing callback
+
+ unsigned int idle_notification;
+ - if set, ->runtime_idle() is being executed
+
+ unsigned int request_pending;
+ - if set, there's a pending request (i.e. a work item queued up into pm_wq)
+
+ enum rpm_request request;
+ - type of request that's pending (valid if request_pending is set)
+
+ unsigned int deferred_resume;
+ - set if ->runtime_resume() is about to be run while ->runtime_suspend() is
+ being executed for that device and it is not practical to wait for the
+ suspend to complete; means "queue up a resume request as soon as you've
+ suspended"
+
+ enum rpm_status runtime_status;
+ - the run-time PM status of the device; this field's initial value is
+ RPM_SUSPENDED, which means that each device is initially regarded by the
+ PM core as 'suspended', regardless of its real hardware status
+
+All of the above fields are members of the 'power' member of 'struct device'.
+
+4. Run-time PM Device Helper Functions
+
+The following run-time PM helper functions are defined in
+drivers/base/power/runtime.c and include/linux/pm_runtime.h:
+
+ void pm_runtime_init(struct device *dev);
+ - initialize the device run-time PM fields in 'struct dev_pm_info'
+
+ void pm_runtime_remove(struct device *dev);
+ - make sure that the run-time PM of the device will be disabled after
+ removing the device from device hierarchy
+
+ int pm_runtime_idle(struct device *dev);
+ - execute ->runtime_idle() for the device's bus type; returns 0 on success
+ or error code on failure, where -EINPROGRESS means that ->runtime_idle()
+ is already being executed
+
+ int pm_runtime_suspend(struct device *dev);
+ - execute ->runtime_suspend() for the device's bus type; returns 0 on
+ success, 1 if the device's run-time PM status was already 'suspended', or
+ error code on failure, where -EAGAIN or -EBUSY means it is safe to attempt
+ to suspend the device again in future
+
+ int pm_runtime_resume(struct device *dev);
+ - execute ->runtime_resume() for the device's bus type; returns 0 on
+ success, 1 if the device's run-time PM status was already 'active' or
+ error code on failure, where -EAGAIN means it may be safe to attempt to
+ resume the device again in future, but 'power.runtime_failure' should be
+ checked additionally
+
+ int pm_request_idle(struct device *dev);
+ - submit a request to execute ->runtime_idle() for the device's bus type
+ (the request is represented by a work item in pm_wq); returns 0 on success
+ or error code if the request has not been queued up
+
+ int pm_schedule_suspend(struct device *dev, unsigned int delay);
+ - schedule the execution of ->runtime_suspend() for the device's bus type
+ in future, where 'delay' is the time to wait before queuing up a suspend
+ work item in pm_wq, in miliseconds (if 'delay' is zero, the work item is
+ queued up immediately); returns 0 on success, 1 if the device's PM
+ run-time status was already 'suspended', or error code if the request
+ hasn't been scheduled (or queued up if 'delay' is 0)
+
+ int pm_request_resume(struct device *dev);
+ - submit a request to execute ->runtime_resume() for the device's bus type
+ (the request is represented by a work item in pm_wq); returns 0 on
+ success, 1 if the device's run-time PM status was already 'active', or
+ error code if the request hasn't been queued up
+
+ void pm_runtime_get_noresume(struct device *dev);
+ - increment the device's usage counter
+
+ int pm_runtime_get(struct device *dev);
+ - increment the device's usage counter, run pm_request_resume(dev) and
+ return its result
+
+ int pm_runtime_get_sync(struct device *dev);
+ - increment the device's usage counter, run pm_rutime_resume(dev) and return
+ its result
+
+ void pm_runtime_put_noidle(struct device *dev);
+ - decrement the device's usage counter
+
+ int pm_runtime_put(struct device *dev);
+ - decrement the device's usage counter, run pm_request_idle(dev) and return
+ its result
+
+ int pm_runtime_put_sync(struct device *dev);
+ - decrement the device's usage counter, run pm_rutime_idle(dev) and return
+ its result
+
+ void pm_runtime_enable(struct device *dev);
+ - enable the run-time PM helper functions to run the device bus type's
+ run-time PM callbacks described in Section 2
+
+ int pm_runtime_disable(struct device *dev);
+ - prevent the run-time PM helper functions from running the device bus
+ type's run-time PM callbacks, make sure that all of the pending run-time
+ PM operations on the device are either completed or canceled; returns
+ 1 if there was a resume request pending and it was necessary to execute
+ ->runtime_resume() for the device's bus type to satisfy that request,
+ otherwise 0 is returned
+
+ void pm_suspend_ignore_children(struct device *dev, bool enable);
+ - set/unset the power.ignore_children flag of the device
+
+ int pm_runtime_set_active(struct device *dev);
+ - clear the device's 'power.runtime_error' flag, set the device's run-time
+ PM status to 'active' and update its parent's counter of 'active'
+ children as appropriate (it is only valid to use this function if
+ 'power.runtime_failure' is set or 'power.disable_depth' is greater than
+ zero); it will fail and return error code if the device has a parent
+ which is not active and the 'power.ignore_children' flag of which is unset
+
+ void pm_runtime_set_suspended(struct device *dev);
+ - clear the device's 'power.runtime_error' flag, set the device's run-time
+ PM status to 'suspended' and update its parent's counter of 'active'
+ children as appropriate (it is only valid to use this function if
+ 'power.runtime_failure' is set or 'power.disable_depth' is greater than
+ zero)
+
+It is safe to execute the following helper functions from interrupt context:
+
+pm_request_idle()
+pm_schedule_suspend()
+pm_request_resume()
+pm_runtime_get_noresume()
+pm_runtime_get()
+pm_runtime_put_noidle()
+pm_runtime_put()
+pm_suspend_ignore_children()
+pm_runtime_set_active()
+pm_runtime_set_suspended()