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>

1 files changed, 33 insertions, 0 deletions

diff --git a/kernel/power/main.c b/kernel/power/main.c
index 428f8a034e96..7beb3fb3670b 100644
--- a/kernel/power/main.c
+++ b/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,