[PATCH 7] PM: Add a switch for disabling/enabling asynchronous suspend/resume

["Rafael J. Wysocki" <rjw@sisk.pl>]

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

Add sysfs attribute kernel/power/pm_async allowing the user space to
disable and enable async suspend/resume of devices.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 drivers/base/power/main.c  |   13 +++++++------
 drivers/base/power/power.h |    6 +++---
 kernel/power/main.c        |   28 +++++++++++++++++++++++++++-
 3 files changed, 37 insertions(+), 10 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 +44,29 @@ 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)
+{
+	int val;
+
+	if (sscanf(buf, "%d", &val) == 1) {
+		pm_async_enabled = !!val;
+		return n;
+	}
+	return -EINVAL;
+}
+
+power_attr(pm_async);
+
 #ifdef CONFIG_PM_DEBUG
 int pm_test_level = TEST_NONE;
 
@@ -208,9 +231,12 @@ 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/main.c
===================================================================
--- linux-2.6.orig/drivers/base/power/main.c
+++ linux-2.6/drivers/base/power/main.c
@@ -235,7 +235,7 @@ static int device_pm_wait_fn(struct devi
  */
 static void device_pm_wait_for_masters(struct device *slave)
 {
-	if (!pm_trace_enabled)
+	if (pm_async_enabled && !pm_trace_enabled)
 		device_for_each_master(slave, slave, device_pm_wait_fn);
 }
 
@@ -245,7 +245,8 @@ static void device_pm_wait_for_masters(s
  */
 static void device_pm_wait_for_slaves(struct device *master)
 {
-	device_for_each_slave(master, master, device_pm_wait_fn);
+	if (pm_async_enabled)
+		device_for_each_slave(master, master, device_pm_wait_fn);
 }
 
 /**
@@ -560,7 +561,7 @@ static int device_resume_noirq(struct de
 	if (pm_op_started(dev))
 		return 0;
 
-	if (dev->power.async_suspend && !pm_trace_enabled) {
+	if (pm_async_enabled && !pm_trace_enabled && dev->power.async_suspend) {
 		async_schedule(async_resume_noirq, dev);
 		return 0;
 	}
@@ -719,7 +720,7 @@ static int device_resume(struct device *
 	if (pm_op_started(dev))
 		return 0;
 
-	if (dev->power.async_suspend && !pm_trace_enabled) {
+	if (pm_async_enabled && !pm_trace_enabled && dev->power.async_suspend) {
 		get_device(dev);
 		async_schedule(async_resume, dev);
 		return 0;
@@ -965,7 +966,7 @@ static int device_suspend_noirq(struct d
 	if (pm_op_started(dev))
 		return 0;
 
-	if (dev->power.async_suspend) {
+	if (pm_async_enabled && dev->power.async_suspend) {
 		async_schedule(async_suspend_noirq, dev);
 		return 0;
 	}
@@ -1139,7 +1140,7 @@ static int device_suspend(struct device 
 	if (pm_op_started(dev))
 		return 0;
 
-	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/drivers/base/power/power.h
===================================================================
--- linux-2.6.orig/drivers/base/power/power.h
+++ linux-2.6/drivers/base/power/power.h
@@ -16,10 +16,10 @@ 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)