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>

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index dcff4d0623add0e7708c642d0cfe210b0c1f48ab..d6a801f45b484e4df433ff09e85a6f3bc07707d5 100644 (file)
--- a/Documentation/ABI/testing/sysfs-power
+++ b/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.

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 3b44c201ddadea01adf6d56b6955722a83874fee..7e79201b09bbab19c3cbe92950e9a9eccdcb95a5 100644 (file)
--- 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 b8fa1aa5225a4a7baff8f1b8f83d46d644f82012..c0bd03c83b9cad1dbbb9341aa70f13e85b520760 100644 (file)
--- 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)

diff --git a/kernel/power/main.c b/kernel/power/main.c
index 0998c7139053c8c5ec46165d32327bba42f2ecce..b58800b21fc01b98fc8af60c2b9ab16385256cc7 100644 (file)
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -44,6 +44,32 @@ int pm_notifier_call_chain(unsigned long val)
                        == 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;
 
@@ -208,8 +234,11 @@ 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,
 };