PM: Add a switch for disabling/enabling asynchronous suspend/resume

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>

2 files changed, 7 insertions, 6 deletions

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 3b44c201ddad..7e79201b09bb 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -201,7 +201,7 @@ static void dpm_wait(struct device *dev, bool async)
         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 *dev)
 {
         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 *dev)
 {
         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;
diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
index b8fa1aa5225a..c0bd03c83b9c 100644
--- a/drivers/base/power/power.h
+++ b/drivers/base/power/power.h
@@ -12,10 +12,10 @@ static inline void pm_runtime_remove(struct device *dev) {}
 
 #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)