Date:	Mon, 8 Jun 2009 13:29:26 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	linux-pm@...ts.linux-foundation.org,
	Alan Stern <stern@...land.harvard.edu>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] Run-time PM idea (was: Re: [RFC][PATCH 0/2] PM: Rearrange core suspend code)

On Monday 08 June 2009, Oliver Neukum wrote:
> Am Sonntag, 7. Juni 2009 23:46:59 schrieb Rafael J. Wysocki:
> > It may be necessary to resume a device synchronously, but I'm still
> > thinking how to implement that.
> 
> This will absolutely be the default. You resume a device because you want
> it to do something now. It seems to me that you making your problem worse
> by using a spinlock as a lock. A mutex would make it easier.

But I need to be able to call __pm_schedule_resume() (at least) from interrupt
context and I can't use a mutex from there.  Otherwise I'd have used a mutex. :-)

Anyway, below is a version with synchronous resume.

Thanks,
Rafael

---
 drivers/base/power/Makefile  |    1 
 drivers/base/power/main.c    |    6 -
 drivers/base/power/runtime.c |  223 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/pm.h           |   36 ++++++
 include/linux/pm_runtime.h   |   82 +++++++++++++++
 kernel/power/Kconfig         |   14 ++
 kernel/power/main.c          |   17 +++
 7 files changed, 376 insertions(+), 3 deletions(-)

Index: linux-2.6/kernel/power/Kconfig
===================================================================
--- linux-2.6.orig/kernel/power/Kconfig
+++ linux-2.6/kernel/power/Kconfig
@@ -204,3 +204,17 @@ 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
+	  responsibile for the actual handling of the autosuspend requests and
+	  wake-up events.
Index: linux-2.6/kernel/power/main.c
===================================================================
--- linux-2.6.orig/kernel/power/main.c
+++ linux-2.6/kernel/power/main.c
@@ -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;
Index: linux-2.6/include/linux/pm.h
===================================================================
--- linux-2.6.orig/include/linux/pm.h
+++ linux-2.6/include/linux/pm.h
@@ -22,6 +22,8 @@
 #define _LINUX_PM_H
 
 #include <linux/list.h>
+#include <linux/workqueue.h>
+#include <linux/spinlock.h>
 
 /*
  * Callbacks for platform drivers to implement.
@@ -165,6 +167,15 @@ 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 two callbacks related to run-time power management of devices:
+ *
+ * @autosuspend: Save the device registers and put it into an energy-saving (low
+ *	power) state at run-time, enable wake-up events as appropriate.
+ *
+ * @autoresume: Put the device into the full power state and restore its
+ *	registers (if applicable) at run time, in response to a wake-up event
+ *	generated by hardware or at a request of software.
  */
 
 struct dev_pm_ops {
@@ -182,6 +193,10 @@ struct dev_pm_ops {
 	int (*thaw_noirq)(struct device *dev);
 	int (*poweroff_noirq)(struct device *dev);
 	int (*restore_noirq)(struct device *dev);
+#ifdef CONFIG_PM_RUNTIME
+	int (*autosuspend)(struct device *dev);
+	int (*autoresume)(struct device *dev);
+#endif
 };
 
 /**
@@ -315,14 +330,31 @@ enum dpm_state {
 	DPM_OFF_IRQ,
 };
 
+enum rpm_state {
+	RPM_UNKNOWN = -1,
+	RPM_ACTIVE,
+	RPM_IDLE,
+	RPM_SUSPENDING,
+	RPM_SUSPENDED,
+};
+
 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
 	struct list_head	entry;
 #endif
+#ifdef	CONFIG_PM_RUNTIME
+	struct delayed_work	suspend_work;
+	struct work_struct	resume_work;
+	unsigned int		suspend_autocancel:1;
+	unsigned int		resume_autocancel:1;
+	unsigned int		suspend_aborted:1;
+	enum rpm_state		runtime_status;
+	spinlock_t		lock;
+#endif
 };
 
 /*
Index: linux-2.6/drivers/base/power/Makefile
===================================================================
--- linux-2.6.orig/drivers/base/power/Makefile
+++ linux-2.6/drivers/base/power/Makefile
@@ -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
Index: linux-2.6/drivers/base/power/runtime.c
===================================================================
--- /dev/null
+++ linux-2.6/drivers/base/power/runtime.c
@@ -0,0 +1,223 @@
+/*
+ * drivers/base/power/runtime.c - Helper functions for device run-time PM
+ *
+ * Copyright (c) 2009 Rafael J. Wysocki <rjw@...k.pl>, Novell Inc.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/pm_runtime.h>
+
+/**
+ * pm_runtime_reset - Clear all of the device run-time PM flags.
+ * @dev: Device object to clear the flags for.
+ */
+static void pm_runtime_reset(struct device *dev)
+{
+	dev->power.resume_autocancel = false;
+	dev->power.suspend_autocancel = false;
+	dev->power.suspend_aborted = false;
+	dev->power.runtime_status = RPM_ACTIVE;
+}
+
+/**
+ * pm_autosuspend - Run autosuspend callback of given device object's bus type.
+ * @work: Work structure used for scheduling the execution of this function.
+ *
+ * Use @work to get the device object the suspend has been scheduled for,
+ * check if the suspend request hasn't been cancelled and run the
+ * ->autosuspend() callback from the device's bus type driver.  Update the
+ * run-time PM flags in the device object to reflect the current status of the
+ * device.
+ */
+static void pm_autosuspend(struct work_struct *work)
+{
+	struct delayed_work *dw = to_delayed_work(work);
+	struct device *dev = suspend_work_to_device(dw);
+	int error = 0;
+
+	pm_lock_device(dev);
+	if (dev->power.suspend_aborted) {
+		dev->power.runtime_status = RPM_ACTIVE;
+		goto out;
+	}
+	dev->power.suspend_autocancel = false;
+	dev->power.runtime_status = RPM_SUSPENDING;
+	pm_unlock_device(dev);
+
+	if (dev && dev->bus && dev->bus->pm && dev->bus->pm->autosuspend)
+		error = dev->bus->pm->autosuspend(dev);
+
+	pm_lock_device(dev);
+	dev->power.runtime_status = error ? RPM_UNKNOWN : RPM_SUSPENDED;
+ out:
+	pm_unlock_device(dev);
+}
+
+/**
+ * __pm_schedule_suspend - Schedule run-time suspend of given device.
+ * @dev: Device to suspend.
+ * @delay: Time to wait before attempting to suspend the device.
+ * @autocancel: If set, the request will be cancelled during a resume from a
+ *	system-wide sleep state if it happens before @delay elapses.
+ */
+void __pm_schedule_suspend(struct device *dev, unsigned long delay,
+			   bool autocancel)
+{
+	pm_lock_device(dev);
+	if (dev->power.runtime_status != RPM_ACTIVE)
+		goto out;
+	dev->power.suspend_autocancel = autocancel;
+	dev->power.suspend_aborted = false;
+	dev->power.runtime_status = RPM_IDLE;
+	queue_delayed_work(pm_wq, &dev->power.suspend_work, delay);
+ out:
+	pm_unlock_device(dev);
+}
+
+/**
+ * pm_autoresume - Run autoresume callback of given device object's bus type.
+ * @work: Work structure used for scheduling the execution of this function.
+ *
+ * Use @work to get the device object the resume has been scheduled for,
+ * check if the device is really suspended and run the ->autoresume() callback
+ * from the device's bus type driver.  Update the run-time PM flags in the
+ * device object to reflect the current status of the device.
+ */
+static void pm_autoresume(struct work_struct *work)
+{
+	struct device *dev = resume_work_to_device(work);
+	int error = 0;
+
+	pm_lock_device(dev);
+	dev->power.resume_autocancel = false;
+	if (dev->power.runtime_status != RPM_SUSPENDED)
+		goto out;
+	pm_unlock_device(dev);
+
+	if (dev->bus && dev->bus->pm && dev->bus->pm->autoresume)
+		error = dev->bus->pm->autoresume(dev);
+
+	pm_lock_device(dev);
+	dev->power.runtime_status = error ? RPM_UNKNOWN : RPM_ACTIVE;
+ out:
+	pm_unlock_device(dev);
+}
+
+/**
+ * pm_cancel_suspend - Cancel a pending suspend request for given device.
+ * @dev: Device to cancel the suspend request for.
+ *
+ * Should be called under pm_lock_device() and only if we are sure that the
+ * ->autosuspend() callback hasn't started to yet.
+ */
+static void pm_cancel_suspend(struct device *dev)
+{
+	dev->power.suspend_autocancel = false;
+	dev->power.suspend_aborted = true;
+	cancel_delayed_work(&dev->power.suspend_work);
+	dev->power.runtime_status = RPM_ACTIVE;
+}
+
+/**
+ * __pm_schedule_resume - Schedule run-time resume of given device.
+ * @dev: Device to resume.
+ * @autocancel: If set, the request will be cancelled during a resume from a
+ *	system-wide sleep state if it happens before pm_autoresume() can be run.
+ */
+void __pm_schedule_resume(struct device *dev, bool autocancel)
+{
+	pm_lock_device(dev);
+	if (dev->power.runtime_status == RPM_IDLE) {
+		/* ->autosuspend() hasn't started yet, no need to resume. */
+		pm_cancel_suspend(dev);
+	} else if (dev->power.runtime_status != RPM_ACTIVE) {
+		dev->power.resume_autocancel = autocancel;
+		queue_work(pm_wq, &dev->power.resume_work);
+	}
+	pm_unlock_device(dev);
+}
+
+/**
+ * pm_resume_sync - Resume given device waiting for the operation to complete.
+ * @dev: Device to resume.
+ *
+ * Resume the device synchronously, waiting for the operation to complete.  If
+ * autosuspend is in progress while this function is being run, wait for it to
+ * finish before resuming the device.  If the autosuspend is scheduled, but it
+ * hasn't started yet, cancel it and we're done.
+ */
+int pm_resume_sync(struct device *dev)
+{
+	int error = 0;
+
+	pm_lock_device(dev);
+	if (dev->power.runtime_status == RPM_IDLE) {
+		/* ->autosuspend() hasn't started yet, no need to resume. */
+		pm_cancel_suspend(dev);
+		goto out;
+	}
+
+	if (dev->power.runtime_status == RPM_SUSPENDING) {
+		/*
+		 * The ->autosuspend() callback is being executed right now,
+		 * wait for it to complete.
+		 */
+		pm_unlock_device(dev);
+		cancel_delayed_work_sync(&dev->power.suspend_work);
+		pm_lock_device(dev);
+	}
+
+	if (dev->power.runtime_status != RPM_SUSPENDED) {
+		error = -EINVAL;
+		goto out;
+	}
+	pm_unlock_device(dev);
+
+	if (dev->bus && dev->bus->pm && dev->bus->pm->autoresume)
+		error = dev->bus->pm->autoresume(dev);
+
+	pm_lock_device(dev);
+	dev->power.runtime_status = error ? RPM_UNKNOWN : RPM_ACTIVE;
+ out:
+	pm_unlock_device(dev);
+
+	return error;
+}
+
+/**
+ * pm_runtime_autocancel - Cancel run-time PM requests during system resume.
+ * @dev: Device to handle.
+ *
+ * If dev->power.suspend_autocancel is set during resume from a system sleep
+ * state, there is a run-time suspend request pending that has to be cancelled,
+ * so cancel it, and analogously for pending run-time resume requests.
+ *
+ * This function is only called by the PM core and must not be used by bus types
+ * and device drivers.  Moreover, it is called when the workqueue is frozen, so
+ * it is guaranteed that the autosuspend callbacks are not running at that time.
+ */
+void pm_runtime_autocancel(struct device *dev)
+{
+	pm_lock_device(dev);
+	if (dev->power.suspend_autocancel) {
+		cancel_delayed_work(&dev->power.suspend_work);
+		pm_runtime_reset(dev);
+	} else if (dev->power.resume_autocancel) {
+		work_clear_pending(&dev->power.resume_work);
+		pm_runtime_reset(dev);
+	}
+	pm_unlock_device(dev);
+}
+
+/**
+ * pm_runtime_init - Initialize run-time PM fields in given device object.
+ * @dev: Device object to handle.
+ */
+void pm_runtime_init(struct device *dev)
+{
+	pm_runtime_reset(dev);
+	spin_lock_init(&dev->power.lock);
+	INIT_DELAYED_WORK(&dev->power.suspend_work, pm_autosuspend);
+	INIT_WORK(&dev->power.resume_work, pm_autoresume);
+}
Index: linux-2.6/include/linux/pm_runtime.h
===================================================================
--- /dev/null
+++ linux-2.6/include/linux/pm_runtime.h
@@ -0,0 +1,82 @@
+/*
+ * pm_runtime.h - Device run-time power management helper functions.
+ *
+ * Copyright (C) 2009 Rafael J. Wysocki <rjw@...k.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_schedule_suspend(struct device *dev, unsigned long delay,
+				   bool autocancel);
+extern void __pm_schedule_resume(struct device *dev, bool autocancel);
+extern void pm_runtime_autocancel(struct device *dev);
+
+static inline struct device *suspend_work_to_device(struct delayed_work *work)
+{
+	struct dev_pm_info *dpi;
+
+	dpi = container_of(work, struct dev_pm_info, suspend_work);
+	return container_of(dpi, struct device, power);
+}
+
+static inline struct device *resume_work_to_device(struct work_struct *work)
+{
+	struct dev_pm_info *dpi;
+
+	dpi = container_of(work, struct dev_pm_info, resume_work);
+	return container_of(dpi, struct device, power);
+}
+
+static inline void pm_lock_device(struct device *dev)
+{
+	spin_lock(&dev->power.lock);
+}
+
+static inline void pm_unlock_device(struct device *dev)
+{
+	spin_unlock(&dev->power.lock);
+}
+#else /* !CONFIG_PM_RUNTIME */
+static inline void pm_runtime_init(struct device *dev) {}
+static inline void __pm_schedule_suspend(struct device *dev,
+					  unsigned long delay,
+					  bool autocancel) {}
+static inline void __pm_schedule_resume(struct device *dev, bool autocancel) {}
+static inline void pm_runtime_autocancel(struct device *dev) {}
+
+static inline void pm_lock_device(struct device *dev) {}
+static inline void pm_unlock_device(struct device *dev) {}
+#endif /* !CONFIG_PM_RUNTIME */
+
+static inline void pm_schedule_suspend(struct device *dev, unsigned long delay)
+{
+	__pm_schedule_suspend(dev, delay, false);
+}
+
+static inline void pm_schedule_suspend_autocancel(struct device *dev,
+						   unsigned long delay)
+{
+	__pm_schedule_suspend(dev, delay, true);
+}
+
+static inline void pm_schedule_resume(struct device *dev)
+{
+	__pm_schedule_resume(dev, false);
+}
+
+static inline void pm_schedule_resume_autocancel(struct device *dev)
+{
+	__pm_schedule_resume(dev, true);
+}
+
+#endif
Index: linux-2.6/drivers/base/power/main.c
===================================================================
--- linux-2.6.orig/drivers/base/power/main.c
+++ linux-2.6/drivers/base/power/main.c
@@ -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>
@@ -88,6 +89,7 @@ void device_pm_add(struct device *dev)
 	}
 
 	list_add_tail(&dev->power.entry, &dpm_list);
+	pm_runtime_init(dev);
 	mutex_unlock(&dpm_list_mtx);
 }
 
@@ -355,7 +357,7 @@ void dpm_resume_noirq(pm_message_t state
 	struct device *dev;
 
 	mutex_lock(&dpm_list_mtx);
-	list_for_each_entry(dev, &dpm_list, power.entry)
+	list_for_each_entry(dev, &dpm_list, power.entry) {
 		if (dev->power.status > DPM_OFF) {
 			int error;
 
@@ -364,6 +366,8 @@ void dpm_resume_noirq(pm_message_t state
 			if (error)
 				pm_dev_err(dev, state, " early", error);
 		}
+		pm_runtime_autocancel(dev);
+	}
 	mutex_unlock(&dpm_list_mtx);
 	resume_device_irqs();
 }
--
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