[PATCH 1/8] PM: Add parent information to timing messages

[PATCH 1/8] PM: Add parent information to timing messages

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Add parent information to the messages printed by the suspend/resume
core when initcall_debug is set.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 drivers/base/power/main.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

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
@@ -271,8 +271,9 @@ static int pm_noirq_op(struct device *de
 	ktime_t calltime, delta, rettime;
 
 	if (initcall_debug) {
-		pr_info("calling  %s_i+ @ %i\n",
-				dev_name(dev), task_pid_nr(current));
+		pr_info("calling  %s+ @ %i, parent: %s\n",
+				dev_name(dev), task_pid_nr(current),
+				dev->parent ? dev_name(dev->parent) : "none");
 		calltime = ktime_get();
 	}
 

[PATCH 2/8] PM: Asynchronous suspend and resume of devices

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Theoretically, the total time of system sleep transitions (suspend
to RAM, hibernation) can be reduced by running suspend and resume
callbacks of device drivers in parallel with each other.  However,
there are dependencies between devices such that we're not allowed
to suspend the parent of a device before suspending the device
itself.  Analogously, we're not allowed to resume a device before
resuming its parent.

The most straightforward way to take these dependencies into accout
is to start the async threads used for suspending and resuming
devices at the core level, so that async_schedule() is called for
each suspend and resume callback supposed to be executed
asynchronously.

For this purpose, introduce a new device flag, power.async_suspend,
used to mark the devices whose suspend and resume callbacks are to be
executed asynchronously (ie. in parallel with the main suspend/resume
thread and possibly in parallel with each other) and helper function
device_enable_async_suspend() allowing one to set power.async_suspend
for given device (power.async_suspend is unset by default for all
devices).  For each device with the power.async_suspend flag set the
PM core will use async_schedule() to execute its suspend and resume
callbacks.

The async threads started for different devices as a result of
calling async_schedule() are synchronized with each other and with
the main suspend/resume thread with the help of completions, in the
following way:
(1) There is a completion, power.completion, for each device object.
(2) Each device's completion is reset before calling async_schedule()
    for the device or, in the case of devices with the
    power.async_suspend flags unset, before executing the device's
    suspend and resume callbacks.
(3) During suspend, right before running the bus type, device type
    and device class suspend callbacks for the device, the PM core
    waits for the completions of all the device's children to be
    completed.
(4) During resume, right before running the bus type, device type and
    device class resume callbacks for the device, the PM core waits
    for the completion of the device's parent to be completed.
(5) The PM core completes power.completion for each device right
    after the bus type, device type and device class suspend (or
    resume) callbacks executed for the device have returned.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 drivers/base/power/main.c    |  115 ++++++++++++++++++++++++++++++++++++++++---
 include/linux/device.h       |    6 ++
 include/linux/pm.h           |    3 +
 include/linux/resume-trace.h |    7 ++
 4 files changed, 125 insertions(+), 6 deletions(-)

Index: linux-2.6/include/linux/pm.h
===================================================================
--- linux-2.6.orig/include/linux/pm.h
+++ linux-2.6/include/linux/pm.h
@@ -26,6 +26,7 @@
 #include <linux/spinlock.h>
 #include <linux/wait.h>
 #include <linux/timer.h>
+#include <linux/completion.h>
 
 /*
  * Callbacks for platform drivers to implement.
@@ -412,9 +413,11 @@ struct dev_pm_info {
 	pm_message_t		power_state;
 	unsigned int		can_wakeup:1;
 	unsigned int		should_wakeup:1;
+	unsigned		async_suspend:1;
 	enum dpm_state		status;		/* Owned by the PM core */
 #ifdef CONFIG_PM_SLEEP
 	struct list_head	entry;
+	struct completion	completion;
 #endif
 #ifdef CONFIG_PM_RUNTIME
 	struct timer_list	suspend_timer;
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
@@ -25,6 +25,7 @@
 #include <linux/resume-trace.h>
 #include <linux/interrupt.h>
 #include <linux/sched.h>
+#include <linux/async.h>
 
 #include "../base.h"
 #include "power.h"
@@ -42,6 +43,7 @@
 LIST_HEAD(dpm_list);
 
 static DEFINE_MUTEX(dpm_list_mtx);
+static pm_message_t pm_transition;
 
 /*
  * Set once the preparation of devices for a PM transition has started, reset
@@ -56,6 +58,7 @@ static bool transition_started;
 void device_pm_init(struct device *dev)
 {
 	dev->power.status = DPM_ON;
+	init_completion(&dev->power.completion);
 	pm_runtime_init(dev);
 }
 
@@ -111,6 +114,7 @@ void device_pm_remove(struct device *dev
 	pr_debug("PM: Removing info for %s:%s\n",
 		 dev->bus ? dev->bus->name : "No Bus",
 		 kobject_name(&dev->kobj));
+	complete_all(&dev->power.completion);
 	mutex_lock(&dpm_list_mtx);
 	list_del_init(&dev->power.entry);
 	mutex_unlock(&dpm_list_mtx);
@@ -188,6 +192,31 @@ static void initcall_debug_report(struct
 }
 
 /**
+ * dpm_wait - Wait for a PM operation to complete.
+ * @dev: Device to wait for.
+ * @async: If unset, wait only if the device's power.async_suspend flag is set.
+ */
+static void dpm_wait(struct device *dev, bool async)
+{
+	if (!dev)
+		return;
+
+	if (async || dev->power.async_suspend)
+		wait_for_completion(&dev->power.completion);
+}
+
+static int dpm_wait_fn(struct device *dev, void *async_ptr)
+{
+	dpm_wait(dev, *((bool *)async_ptr));
+	return 0;
+}
+
+static void dpm_wait_for_children(struct device *dev, bool async)
+{
+       device_for_each_child(dev, &async, dpm_wait_fn);
+}
+
+/**
  * pm_op - Execute the PM operation appropriate for given PM event.
  * @dev: Device to handle.
  * @ops: PM operations to choose from.
@@ -466,17 +495,19 @@ static int legacy_resume(struct device *
 }
 
 /**
- * device_resume - Execute "resume" callbacks for given device.
+ * __device_resume - Execute "resume" callbacks for given device.
  * @dev: Device to handle.
  * @state: PM transition of the system being carried out.
+ * @async: If true, the device is being resumed asynchronously.
  */
-static int device_resume(struct device *dev, pm_message_t state)
+static int __device_resume(struct device *dev, pm_message_t state, bool async)
 {
 	int error = 0;
 
 	TRACE_DEVICE(dev);
 	TRACE_RESUME(0);
 
+	dpm_wait(dev->parent, async);
 	down(&dev->sem);
 
 	if (dev->bus) {
@@ -511,11 +542,36 @@ static int device_resume(struct device *
 	}
  End:
 	up(&dev->sem);
+	complete_all(&dev->power.completion);
 
 	TRACE_RESUME(error);
 	return error;
 }
 
+static void async_resume(void *data, async_cookie_t cookie)
+{
+	struct device *dev = (struct device *)data;
+	int error;
+
+	error = __device_resume(dev, pm_transition, true);
+	if (error)
+		pm_dev_err(dev, pm_transition, " async", error);
+	put_device(dev);
+}
+
+static int device_resume(struct device *dev)
+{
+	INIT_COMPLETION(dev->power.completion);
+
+	if (dev->power.async_suspend && !pm_trace_is_enabled()) {
+		get_device(dev);
+		async_schedule(async_resume, dev);
+		return 0;
+	}
+
+	return __device_resume(dev, pm_transition, false);
+}
+
 /**
  * dpm_resume - Execute "resume" callbacks for non-sysdev devices.
  * @state: PM transition of the system being carried out.
@@ -530,6 +586,7 @@ static void dpm_resume(pm_message_t stat
 
 	INIT_LIST_HEAD(&list);
 	mutex_lock(&dpm_list_mtx);
+	pm_transition = state;
 	while (!list_empty(&dpm_list)) {
 		struct device *dev = to_device(dpm_list.next);
 
@@ -540,7 +597,7 @@ static void dpm_resume(pm_message_t stat
 			dev->power.status = DPM_RESUMING;
 			mutex_unlock(&dpm_list_mtx);
 
-			error = device_resume(dev, state);
+			error = device_resume(dev);
 
 			mutex_lock(&dpm_list_mtx);
 			if (error)
@@ -555,6 +612,7 @@ static void dpm_resume(pm_message_t stat
 	}
 	list_splice(&list, &dpm_list);
 	mutex_unlock(&dpm_list_mtx);
+	async_synchronize_full();
 	dpm_show_time(starttime, state, NULL);
 }
 
@@ -732,17 +790,24 @@ static int legacy_suspend(struct device 
 	return error;
 }
 
+static int async_error;
+
 /**
  * device_suspend - Execute "suspend" callbacks for given device.
  * @dev: Device to handle.
  * @state: PM transition of the system being carried out.
+ * @async: If true, the device is being suspended asynchronously.
  */
-static int device_suspend(struct device *dev, pm_message_t state)
+static int __device_suspend(struct device *dev, pm_message_t state, bool async)
 {
 	int error = 0;
 
+	dpm_wait_for_children(dev, async);
 	down(&dev->sem);
 
+	if (async_error)
+		goto End;
+
 	if (dev->class) {
 		if (dev->class->pm) {
 			pm_dev_dbg(dev, state, "class ");
@@ -773,12 +838,44 @@ static int device_suspend(struct device 
 			error = legacy_suspend(dev, state, dev->bus->suspend);
 		}
 	}
+
+	if (!error)
+		dev->power.status = DPM_OFF;
+
  End:
 	up(&dev->sem);
+	complete_all(&dev->power.completion);
 
 	return error;
 }
 
+static void async_suspend(void *data, async_cookie_t cookie)
+{
+	struct device *dev = (struct device *)data;
+	int error;
+
+	error = __device_suspend(dev, pm_transition, true);
+	if (error) {
+		pm_dev_err(dev, pm_transition, " async", error);
+		async_error = error;
+	}
+
+	put_device(dev);
+}
+
+static int device_suspend(struct device *dev)
+{
+	INIT_COMPLETION(dev->power.completion);
+
+	if (dev->power.async_suspend) {
+		get_device(dev);
+		async_schedule(async_suspend, dev);
+		return 0;
+	}
+
+	return __device_suspend(dev, pm_transition, false);
+}
+
 /**
  * dpm_suspend - Execute "suspend" callbacks for all non-sysdev devices.
  * @state: PM transition of the system being carried out.
@@ -791,13 +888,15 @@ static int dpm_suspend(pm_message_t stat
 
 	INIT_LIST_HEAD(&list);
 	mutex_lock(&dpm_list_mtx);
+	pm_transition = state;
+	async_error = 0;
 	while (!list_empty(&dpm_list)) {
 		struct device *dev = to_device(dpm_list.prev);
 
 		get_device(dev);
 		mutex_unlock(&dpm_list_mtx);
 
-		error = device_suspend(dev, state);
+		error = device_suspend(dev);
 
 		mutex_lock(&dpm_list_mtx);
 		if (error) {
@@ -805,13 +904,17 @@ static int dpm_suspend(pm_message_t stat
 			put_device(dev);
 			break;
 		}
-		dev->power.status = DPM_OFF;
 		if (!list_empty(&dev->power.entry))
 			list_move(&dev->power.entry, &list);
 		put_device(dev);
+		if (async_error)
+			break;
 	}
 	list_splice(&list, dpm_list.prev);
 	mutex_unlock(&dpm_list_mtx);
+	async_synchronize_full();
+	if (!error)
+		error = async_error;
 	if (!error)
 		dpm_show_time(starttime, state, NULL);
 	return error;
Index: linux-2.6/include/linux/resume-trace.h
===================================================================
--- linux-2.6.orig/include/linux/resume-trace.h
+++ linux-2.6/include/linux/resume-trace.h
@@ -6,6 +6,11 @@
 
 extern int pm_trace_enabled;
 
+static inline int pm_trace_is_enabled(void)
+{
+       return pm_trace_enabled;
+}
+
 struct device;
 extern void set_trace_device(struct device *);
 extern void generate_resume_trace(const void *tracedata, unsigned int user);
@@ -17,6 +22,8 @@ extern void generate_resume_trace(const 
 
 #else
 
+static inline int pm_trace_is_enabled(void) { return 0; }
+
 #define TRACE_DEVICE(dev) do { } while (0)
 #define TRACE_RESUME(dev) do { } while (0)
 
Index: linux-2.6/include/linux/device.h
===================================================================
--- linux-2.6.orig/include/linux/device.h
+++ linux-2.6/include/linux/device.h
@@ -472,6 +472,12 @@ static inline int device_is_registered(s
 	return dev->kobj.state_in_sysfs;
 }
 
+static inline void device_enable_async_suspend(struct device *dev)
+{
+	if (dev->power.status == DPM_ON)
+		dev->power.async_suspend = true;
+}
+
 void driver_init(void);
 
 /*

[PATCH 3/8] PM: Add a switch for disabling/enabling asynchronous suspend/resume

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Add sysfs attribute /sys/power/pm_async allowing the user space to
disable/enable asynchronous suspend/resume of devices.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 Documentation/ABI/testing/sysfs-power |   13 +++++++++++++
 drivers/base/power/main.c             |    7 ++++---
 drivers/base/power/power.h            |    6 +++---
 kernel/power/main.c                   |   31 ++++++++++++++++++++++++++++++-
 4 files changed, 50 insertions(+), 7 deletions(-)

Index: linux-2.6/kernel/power/main.c
===================================================================
--- linux-2.6.orig/kernel/power/main.c
+++ linux-2.6/kernel/power/main.c
@@ -44,6 +44,32 @@ int pm_notifier_call_chain(unsigned long
 			== NOTIFY_BAD) ? -EINVAL : 0;
 }
 
+/* If set, devices may be suspended and resumed asynchronously. */
+int pm_async_enabled = 1;
+
+static ssize_t pm_async_show(struct kobject *kobj, struct kobj_attribute *attr,
+			     char *buf)
+{
+	return sprintf(buf, "%d\n", pm_async_enabled);
+}
+
+static ssize_t pm_async_store(struct kobject *kobj, struct kobj_attribute *attr,
+			      const char *buf, size_t n)
+{
+	unsigned long val;
+
+	if (strict_strtoul(buf, 10, &val))
+		return -EINVAL;
+
+	if (val > 1)
+		return -EINVAL;
+
+	pm_async_enabled = val;
+	return n;
+}
+
+power_attr(pm_async);
+
 #ifdef CONFIG_PM_DEBUG
 int pm_test_level = TEST_NONE;
 
@@ -208,9 +234,12 @@ static struct attribute * g[] = {
 #ifdef CONFIG_PM_TRACE
 	&pm_trace_attr.attr,
 #endif
-#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_PM_DEBUG)
+#ifdef CONFIG_PM_SLEEP
+	&pm_async_attr.attr,
+#ifdef CONFIG_PM_DEBUG
 	&pm_test_attr.attr,
 #endif
+#endif
 	NULL,
 };
 
Index: linux-2.6/drivers/base/power/power.h
===================================================================
--- linux-2.6.orig/drivers/base/power/power.h
+++ linux-2.6/drivers/base/power/power.h
@@ -12,10 +12,10 @@ static inline void pm_runtime_remove(str
 
 #ifdef CONFIG_PM_SLEEP
 
-/*
- * main.c
- */
+/* kernel/power/main.c */
+extern int pm_async_enabled;
 
+/* drivers/base/power/main.c */
 extern struct list_head dpm_list;	/* The active device list */
 
 static inline struct device *to_device(struct list_head *entry)
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
@@ -201,7 +201,7 @@ static void dpm_wait(struct device *dev,
 	if (!dev)
 		return;
 
-	if (async || dev->power.async_suspend)
+	if (async || (pm_async_enabled && dev->power.async_suspend))
 		wait_for_completion(&dev->power.completion);
 }
 
@@ -563,7 +563,8 @@ static int device_resume(struct device *
 {
 	INIT_COMPLETION(dev->power.completion);
 
-	if (dev->power.async_suspend && !pm_trace_is_enabled()) {
+	if (pm_async_enabled && dev->power.async_suspend
+	    && !pm_trace_is_enabled()) {
 		get_device(dev);
 		async_schedule(async_resume, dev);
 		return 0;
@@ -867,7 +868,7 @@ static int device_suspend(struct device 
 {
 	INIT_COMPLETION(dev->power.completion);
 
-	if (dev->power.async_suspend) {
+	if (pm_async_enabled && dev->power.async_suspend) {
 		get_device(dev);
 		async_schedule(async_suspend, dev);
 		return 0;
Index: linux-2.6/Documentation/ABI/testing/sysfs-power
===================================================================
--- linux-2.6.orig/Documentation/ABI/testing/sysfs-power
+++ linux-2.6/Documentation/ABI/testing/sysfs-power
@@ -101,3 +101,16 @@ Description:
 
 		CAUTION: Using it will cause your machine's real-time (CMOS)
 		clock to be set to a random invalid time after a resume.
+
+What:		/sys/power/pm_async
+Date:		January 2009
+Contact:	Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+		The /sys/power/pm_async file controls the switch allowing the
+		user space to enable or disable asynchronous suspend and resume
+		of devices.  If enabled, this feature will cause some device
+		drivers' suspend and resume callbacks to be executed in parallel
+		with each other and with the main suspend thread.  It is enabled
+		if this file contains "1", which is the default.  It may be
+		disabled by writing "0" to this file, in which case all devices
+		will be suspended and resumed synchronously.

[PATCH 4/8] PM: Add facility for advanced testing of async suspend/resume

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Add configuration switch CONFIG_PM_ADVANCED_DEBUG for compiling in
extra PM debugging/testing code allowing one to access some
PM-related attributes of devices from the user space via sysfs.

If CONFIG_PM_ADVANCED_DEBUG is set, add sysfs attribute power/async
for every device allowing the user space to access the device's
power.async_suspend flag and modify it, if desired.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 Documentation/ABI/testing/sysfs-devices-power |   26 +++++++++++++
 drivers/base/power/sysfs.c                    |   49 ++++++++++++++++++++++++++
 include/linux/device.h                        |   11 +++++
 kernel/power/Kconfig                          |   14 +++++++
 4 files changed, 100 insertions(+)

Index: linux-2.6/drivers/base/power/sysfs.c
===================================================================
--- linux-2.6.orig/drivers/base/power/sysfs.c
+++ linux-2.6/drivers/base/power/sysfs.c
@@ -54,6 +54,24 @@
  *	wakeup events internally (unless they are disabled), keeping
  *	their hardware in low power modes whenever they're unused.  This
  *	saves runtime power, without requiring system-wide sleep states.
+ *
+ *	async - Report/change current async suspend setting for the device
+ *
+ *	Asynchronous suspend and resume of the device during system-wide power
+ *	state transitions can be enabled by writing "enabled" to this file.
+ *	Analogously, if "disabled" is written to this file, the device will be
+ *	suspended and resumed synchronously.
+ *
+ *	All devices have one of the following two values for power/async:
+ *
+ *	 + "enabled\n" to permit the asynchronous suspend/resume of the device;
+ *	 + "disabled\n" to forbid it;
+ *
+ *	NOTE: It generally is unsafe to permit the asynchronous suspend/resume
+ *	of a device unless it is certain that all of the PM dependencies of the
+ *	device are known to the PM core.  However, for some devices this
+ *	attribute is set to "enabled" by bus type code or device drivers and in
+ *	that cases it should be safe to leave the default value.
  */
 
 static const char enabled[] = "enabled";
@@ -125,12 +143,43 @@ wake_store(struct device * dev, struct d
 
 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
 
+#ifdef CONFIG_PM_SLEEP_ADVANCED_DEBUG
+static ssize_t async_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	return sprintf(buf, "%s\n",
+			device_async_suspend_enabled(dev) ? enabled : disabled);
+}
+
+static ssize_t async_store(struct device *dev, struct device_attribute *attr,
+			   const char *buf, size_t n)
+{
+	char *cp;
+	int len = n;
+
+	cp = memchr(buf, '\n', n);
+	if (cp)
+		len = cp - buf;
+	if (len == sizeof enabled - 1 && strncmp(buf, enabled, len) == 0)
+		device_enable_async_suspend(dev);
+	else if (len == sizeof disabled - 1 && strncmp(buf, disabled, len) == 0)
+		device_disable_async_suspend(dev);
+	else
+		return -EINVAL;
+	return n;
+}
+
+static DEVICE_ATTR(async, 0644, async_show, async_store);
+#endif /* CONFIG_PM_SLEEP_ADVANCED_DEBUG */
 
 static struct attribute * power_attrs[] = {
 #ifdef CONFIG_PM_RUNTIME
 	&dev_attr_control.attr,
 #endif
 	&dev_attr_wakeup.attr,
+#ifdef CONFIG_PM_SLEEP_ADVANCED_DEBUG
+	&dev_attr_async.attr,
+#endif
 	NULL,
 };
 static struct attribute_group pm_attr_group = {
Index: linux-2.6/include/linux/device.h
===================================================================
--- linux-2.6.orig/include/linux/device.h
+++ linux-2.6/include/linux/device.h
@@ -478,6 +478,17 @@ static inline void device_enable_async_s
 		dev->power.async_suspend = true;
 }
 
+static inline void device_disable_async_suspend(struct device *dev)
+{
+	if (dev->power.status == DPM_ON)
+		dev->power.async_suspend = false;
+}
+
+static inline bool device_async_suspend_enabled(struct device *dev)
+{
+	return !!dev->power.async_suspend;
+}
+
 void driver_init(void);
 
 /*
Index: linux-2.6/kernel/power/Kconfig
===================================================================
--- linux-2.6.orig/kernel/power/Kconfig
+++ linux-2.6/kernel/power/Kconfig
@@ -27,6 +27,15 @@ config PM_DEBUG
 	code. This is helpful when debugging and reporting PM bugs, like
 	suspend support.
 
+config PM_ADVANCED_DEBUG
+	bool "Extra PM attributes in sysfs for low-level debugging/testing"
+	depends on PM_DEBUG
+	default n
+	---help---
+	Add extra sysfs attributes allowing one to access some Power Management
+	fields of device objects from user space.  If you are not a kernel
+	developer interested in debugging/testing Power Management, say "no".
+
 config PM_VERBOSE
 	bool "Verbose Power Management debugging"
 	depends on PM_DEBUG
@@ -85,6 +94,11 @@ config PM_SLEEP
 	depends on SUSPEND || HIBERNATION || XEN_SAVE_RESTORE
 	default y
 
+config PM_SLEEP_ADVANCED_DEBUG
+	bool
+	depends on PM_ADVANCED_DEBUG
+	default n
+
 config SUSPEND
 	bool "Suspend to RAM and standby"
 	depends on PM && ARCH_SUSPEND_POSSIBLE
Index: linux-2.6/Documentation/ABI/testing/sysfs-devices-power
===================================================================
--- linux-2.6.orig/Documentation/ABI/testing/sysfs-devices-power
+++ linux-2.6/Documentation/ABI/testing/sysfs-devices-power
@@ -51,3 +51,29 @@ Description:
 		drivers.  Changing this attribute to "on" prevents the driver
 		from power managing the device at run time.  Doing that while
 		the device is suspended causes it to be woken up.
+
+What:		/sys/devices/.../power/async
+Date:		January 2009
+Contact:	Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+		The /sys/devices/.../async attribute allows the user space to
+		enable or diasble the device's suspend and resume callbacks to
+		be executed asynchronously (ie. in separate threads, in parallel
+		with the main suspend/resume thread) during system-wide power
+		transitions (eg. suspend to RAM, hibernation).
+
+		All devices have one of the following two values for the
+		power/async file:
+
+		+ "enabled\n" to permit the asynchronous suspend/resume;
+		+ "disabled\n" to forbid it;
+
+		The value of this attribute may be changed by writing either
+		"enabled", or "disabled" to it.
+
+		It generally is unsafe to permit the asynchronous suspend/resume
+		of a device unless it is certain that all of the PM dependencies
+		of the device are known to the PM core.  However, for some
+		devices this attribute is set to "enabled" by bus type code or
+		device drivers and in that cases it should be safe to leave the
+		default value.

[PATCH 5/8] PM: Start asynchronous resume threads upfront

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

It has been shown by testing that total device resume time can be
reduced significantly (by as much as 50% or more) if the async
threads executing some devices' resume routines are all started
before the main resume thread starts to handle the "synchronous"
devices.

This is a consequence of the fact that the slowest devices tend to be
located at the end of dpm_list, so their resume routines are started
very late.  Consequently, they have to wait for all the preceding
"synchronous" devices before their resume routines can be started
by the main resume thread, even if they are "asynchronous".  By
starting their async threads upfront we effectively move those
devices towards the beginning of dpm_list, without breaking their
ordering with respect to their parents and children.  As a result,
their resume routines are started much earlier and we are able to
save much more device resume time this way.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 drivers/base/power/main.c |   43 ++++++++++++++++++++++++-------------------
 1 file changed, 24 insertions(+), 19 deletions(-)

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
@@ -495,12 +495,12 @@ static int legacy_resume(struct device *
 }
 
 /**
- * __device_resume - Execute "resume" callbacks for given device.
+ * device_resume - Execute "resume" callbacks for given device.
  * @dev: Device to handle.
  * @state: PM transition of the system being carried out.
  * @async: If true, the device is being resumed asynchronously.
  */
-static int __device_resume(struct device *dev, pm_message_t state, bool async)
+static int device_resume(struct device *dev, pm_message_t state, bool async)
 {
 	int error = 0;
 
@@ -510,6 +510,8 @@ static int __device_resume(struct device
 	dpm_wait(dev->parent, async);
 	down(&dev->sem);
 
+	dev->power.status = DPM_RESUMING;
+
 	if (dev->bus) {
 		if (dev->bus->pm) {
 			pm_dev_dbg(dev, state, "");
@@ -553,24 +555,16 @@ static void async_resume(void *data, asy
 	struct device *dev = (struct device *)data;
 	int error;
 
-	error = __device_resume(dev, pm_transition, true);
+	error = device_resume(dev, pm_transition, true);
 	if (error)
 		pm_dev_err(dev, pm_transition, " async", error);
 	put_device(dev);
 }
 
-static int device_resume(struct device *dev)
+static bool is_async(struct device *dev)
 {
-	INIT_COMPLETION(dev->power.completion);
-
-	if (pm_async_enabled && dev->power.async_suspend
-	    && !pm_trace_is_enabled()) {
-		get_device(dev);
-		async_schedule(async_resume, dev);
-		return 0;
-	}
-
-	return __device_resume(dev, pm_transition, false);
+	return dev->power.async_suspend && pm_async_enabled
+		&& !pm_trace_is_enabled();
 }
 
 /**
@@ -583,22 +577,33 @@ static int device_resume(struct device *
 static void dpm_resume(pm_message_t state)
 {
 	struct list_head list;
+	struct device *dev;
 	ktime_t starttime = ktime_get();
 
 	INIT_LIST_HEAD(&list);
 	mutex_lock(&dpm_list_mtx);
 	pm_transition = state;
-	while (!list_empty(&dpm_list)) {
-		struct device *dev = to_device(dpm_list.next);
 
+	list_for_each_entry(dev, &dpm_list, power.entry) {
+		if (dev->power.status < DPM_OFF)
+			continue;
+
+		INIT_COMPLETION(dev->power.completion);
+		if (is_async(dev)) {
+			get_device(dev);
+			async_schedule(async_resume, dev);
+		}
+	}
+
+	while (!list_empty(&dpm_list)) {
+		dev = to_device(dpm_list.next);
 		get_device(dev);
-		if (dev->power.status >= DPM_OFF) {
+		if (dev->power.status >= DPM_OFF && !is_async(dev)) {
 			int error;
 
-			dev->power.status = DPM_RESUMING;
 			mutex_unlock(&dpm_list_mtx);
 
-			error = device_resume(dev);
+			error = device_resume(dev, state, false);
 
 			mutex_lock(&dpm_list_mtx);
 			if (error)

[PATCH 6/8] PM: Allow PCI devices to suspend/resume asynchronously

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Set power.async_suspend for all PCI devices and PCIe port services,
so that they can be suspended and resumed in parallel with other
devices they don't depend on in a known way (i.e. devices which are
not their parents or children).

This only affects the "regular" suspend and resume stages, which
means in particular that the restoration of the PCI devices' standard
configuration registers during resume will still be carried out
synchronously (at the "early" resume stage).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 drivers/pci/pci.c               |    1 +
 drivers/pci/pcie/portdrv_core.c |    1 +
 drivers/pci/probe.c             |    1 +
 3 files changed, 3 insertions(+)

Index: linux-2.6/drivers/pci/pci.c
===================================================================
--- linux-2.6.orig/drivers/pci/pci.c
+++ linux-2.6/drivers/pci/pci.c
@@ -1541,6 +1541,7 @@ void pci_pm_init(struct pci_dev *dev)
 	int pm;
 	u16 pmc;
 
+	device_enable_async_suspend(&dev->dev);
 	dev->wakeup_prepared = false;
 	dev->pm_cap = 0;
 
Index: linux-2.6/drivers/pci/pcie/portdrv_core.c
===================================================================
--- linux-2.6.orig/drivers/pci/pcie/portdrv_core.c
+++ linux-2.6/drivers/pci/pcie/portdrv_core.c
@@ -285,6 +285,7 @@ static int pcie_device_init(struct pci_d
 		     pci_name(pdev),
 		     get_descriptor_id(pdev->pcie_type, service));
 	device->parent = &pdev->dev;
+	device_enable_async_suspend(device);
 
 	retval = device_register(device);
 	if (retval)
Index: linux-2.6/drivers/pci/probe.c
===================================================================
--- linux-2.6.orig/drivers/pci/probe.c
+++ linux-2.6/drivers/pci/probe.c
@@ -1200,6 +1200,7 @@ struct pci_bus * pci_create_bus(struct d
 	if (error)
 		goto dev_reg_err;
 	b->bridge = get_device(dev);
+	device_enable_async_suspend(b->bridge);
 
 	if (!parent)
 		set_dev_node(b->bridge, pcibus_to_node(b));

[PATCH 7/8] PM: Allow USB devices to suspend/resume asynchronously

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Set power.async_suspend for USB devices, endpoints and interfaces,
allowing them to be suspended and resumed asynchronously during
system sleep transitions.

The power.async_suspend flag is also set for devices that don't have
suspend or resume callbacks, because otherwise they would make the
main suspend/resume thread wait for their "asynchronous" children
(during suspend) or parents (during resume), effectively negating the
possible gains from executing these devices' suspend and resume
callbacks asynchronously.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 drivers/usb/core/endpoint.c |    1 +
 drivers/usb/core/hcd-pci.c  |    1 +
 drivers/usb/core/hub.c      |    1 +
 drivers/usb/core/message.c  |    1 +
 4 files changed, 4 insertions(+)

Index: linux-2.6/drivers/usb/core/hub.c
===================================================================
--- linux-2.6.orig/drivers/usb/core/hub.c
+++ linux-2.6/drivers/usb/core/hub.c
@@ -1817,6 +1817,7 @@ int usb_new_device(struct usb_device *ud
 	/* Tell the world! */
 	announce_device(udev);
 
+	device_enable_async_suspend(&udev->dev);
 	/* Register the device.  The device driver is responsible
 	 * for configuring the device and invoking the add-device
 	 * notifier chain (used by usbfs and possibly others).
Index: linux-2.6/drivers/usb/core/message.c
===================================================================
--- linux-2.6.orig/drivers/usb/core/message.c
+++ linux-2.6/drivers/usb/core/message.c
@@ -1867,6 +1867,7 @@ free_interfaces:
 			"adding %s (config #%d, interface %d)\n",
 			dev_name(&intf->dev), configuration,
 			intf->cur_altsetting->desc.bInterfaceNumber);
+		device_enable_async_suspend(&intf->dev);
 		ret = device_add(&intf->dev);
 		if (ret != 0) {
 			dev_err(&dev->dev, "device_add(%s) --> %d\n",
Index: linux-2.6/drivers/usb/core/endpoint.c
===================================================================
--- linux-2.6.orig/drivers/usb/core/endpoint.c
+++ linux-2.6/drivers/usb/core/endpoint.c
@@ -186,6 +186,7 @@ int usb_create_ep_devs(struct device *pa
 	ep_dev->dev.parent = parent;
 	ep_dev->dev.release = ep_device_release;
 	dev_set_name(&ep_dev->dev, "ep_%02x", endpoint->desc.bEndpointAddress);
+	device_enable_async_suspend(&ep_dev->dev);
 
 	retval = device_register(&ep_dev->dev);
 	if (retval)

[PATCH 8/8] PM: Allow SCSI devices to suspend/resume asynchronously

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rjw@sisk.pl>

Set power.async_suspend for all SCSI devices, targets and hosts, so
that they can be suspended and resumed in parallel with the main
suspend/resume thread and possibly with other devices they don't
depend on in a known way (i.e. devices which are not their parents or
children).

The power.async_suspend flag is also set for devices that don't have
suspend or resume callbacks, because otherwise they would make the
main suspend/resume thread wait for their "asynchronous" children
(during suspend) or parents (during resume), effectively negating the
possible gains from executing these devices' suspend and resume
callbacks asynchronously.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 drivers/scsi/hosts.c      |    4 ++++
 drivers/scsi/scsi_sysfs.c |    4 ++++
 2 files changed, 8 insertions(+)

Index: linux-2.6/drivers/scsi/hosts.c
===================================================================
--- linux-2.6.orig/drivers/scsi/hosts.c
+++ linux-2.6/drivers/scsi/hosts.c
@@ -215,6 +215,8 @@ int scsi_add_host_with_dma(struct Scsi_H
 		shost->shost_gendev.parent = dev ? dev : &platform_bus;
 	shost->dma_dev = dma_dev;
 
+	device_enable_async_suspend(&shost->shost_gendev);
+
 	error = device_add(&shost->shost_gendev);
 	if (error)
 		goto out;
@@ -222,6 +224,8 @@ int scsi_add_host_with_dma(struct Scsi_H
 	scsi_host_set_state(shost, SHOST_RUNNING);
 	get_device(shost->shost_gendev.parent);
 
+	device_enable_async_suspend(&shost->shost_dev);
+
 	error = device_add(&shost->shost_dev);
 	if (error)
 		goto out_del_gendev;
Index: linux-2.6/drivers/scsi/scsi_sysfs.c
===================================================================
--- linux-2.6.orig/drivers/scsi/scsi_sysfs.c
+++ linux-2.6/drivers/scsi/scsi_sysfs.c
@@ -847,6 +847,8 @@ static int scsi_target_add(struct scsi_t
 	if (starget->state != STARGET_CREATED)
 		return 0;
 
+	device_enable_async_suspend(&starget->dev);
+
 	error = device_add(&starget->dev);
 	if (error) {
 		dev_err(&starget->dev, "target device_add failed, error %d\n", error);
@@ -886,11 +888,13 @@ int scsi_sysfs_add_sdev(struct scsi_devi
 		return error;
 
 	transport_configure_device(&starget->dev);
+	device_enable_async_suspend(&sdev->sdev_gendev);
 	error = device_add(&sdev->sdev_gendev);
 	if (error) {
 		printk(KERN_INFO "error 1\n");
 		goto out_remove;
 	}
+	device_enable_async_suspend(&sdev->sdev_dev);
 	error = device_add(&sdev->sdev_dev);
 	if (error) {
 		printk(KERN_INFO "error 2\n");

Re: [PATCH 1/8] PM: Add parent information to timing messages

[Pavel Machek]

On Sun 2010-01-24 00:34:36, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@sisk.pl>
> 
> Add parent information to the messages printed by the suspend/resume
> core when initcall_debug is set.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

ACK.

-- 
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