[PATCH 4/5] 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  |    7 ++++---
 drivers/base/power/power.h |    6 +++---
 kernel/power/main.c        |   31 ++++++++++++++++++++++++++++++-
 3 files changed, 37 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
@@ -175,7 +175,7 @@ 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);
 }
 
@@ -521,7 +521,8 @@ 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;
@@ -806,7 +807,7 @@ 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;