PM / Sleep: add knob for printing device resume times

Added a new knob called /sys/power/pm_print_times. Setting it to 1
enables printing of time taken by devices to suspend and resume.
Setting it to 0 disables this printing (unless overridden by
initcall_debug kernel command line option).

Signed-off-by: Sameer Nanda <snanda@chromium.org>
Acked-by: Greg KH <gregkh@linuxfoundation.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

Documentation/ABI/testing/sysfs-power

@@ -231,3 +231,16 @@ Description:
 		Reads from this file return a string consisting of the names of
 		wakeup sources created with the help of /sys/power/wake_lock
 		that are inactive at the moment, separated with spaces.
+
+What:		/sys/power/pm_print_times
+Date:		May 2012
+Contact:	Sameer Nanda <snanda@chromium.org>
+Description:
+		The /sys/power/pm_print_times file allows user space to
+		control whether the time taken by devices to suspend and
+		resume is printed.  These prints are useful for hunting down
+		devices that take too long to suspend or resume.
+
+		Writing a "1" enables this printing while writing a "0"
+		disables it.  The default value is "0".  Reading from this file
+		will display the current value.

drivers/base/power/main.c

@@ -166,7 +166,7 @@ static ktime_t initcall_debug_start(struct device *dev)
 {
 	ktime_t calltime = ktime_set(0, 0);
 
-	if (initcall_debug) {
+	if (pm_print_times) {
 		pr_info("calling  %s+ @ %i, parent: %s\n",
 			dev_name(dev), task_pid_nr(current),
 			dev->parent ? dev_name(dev->parent) : "none");
@@ -181,7 +181,7 @@ static void initcall_debug_report(struct device *dev, ktime_t calltime,
 {
 	ktime_t delta, rettime;
 
-	if (initcall_debug) {
+	if (pm_print_times) {
 		rettime = ktime_get();
 		delta = ktime_sub(rettime, calltime);
 		pr_info("call %s+ returned %d after %Ld usecs\n", dev_name(dev),

drivers/base/power/power.h

@@ -85,3 +85,14 @@ static inline int pm_qos_sysfs_add(struct device *dev) { return 0; }
 static inline void pm_qos_sysfs_remove(struct device *dev) {}
 
 #endif
+
+#ifdef CONFIG_PM_DEBUG
+
+extern int pm_print_times_enabled;
+#define pm_print_times (initcall_debug || pm_print_times_enabled)
+
+#else /* CONFIG_PM_DEBUG */
+
+#define pm_print_times initcall_debug
+
+#endif /* CONFIG_PM_DEBUG */

kernel/power/main.c

@@ -132,6 +132,38 @@ static ssize_t pm_test_store(struct kobject *kobj, struct kobj_attribute *attr,
 }
 
 power_attr(pm_test);
+
+/*
+ * pm_print_times: print time taken by devices to suspend and resume.
+ *
+ * show() returns whether printing of suspend and resume times is enabled.
+ * store() accepts 0 or 1.  0 disables printing and 1 enables it.
+ */
+int pm_print_times_enabled;
+
+static ssize_t pm_print_times_show(struct kobject *kobj,
+				   struct kobj_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", pm_print_times_enabled);
+}
+
+static ssize_t pm_print_times_store(struct kobject *kobj,
+				    struct kobj_attribute *attr,
+				    const char *buf, size_t n)
+{
+	unsigned long val;
+
+	if (kstrtoul(buf, 10, &val))
+		return -EINVAL;
+
+	if (val > 1)
+		return -EINVAL;
+
+	pm_print_times_enabled = val;
+	return n;
+}
+
+power_attr(pm_print_times);
 #endif /* CONFIG_PM_DEBUG */
 
 #ifdef CONFIG_DEBUG_FS
@@ -530,6 +562,7 @@ static struct attribute * g[] = {
 #endif
 #ifdef CONFIG_PM_DEBUG
 	&pm_test_attr.attr,
+	&pm_print_times_attr.attr,
 #endif
 #endif
 	NULL,