PM / sleep: Report interrupt that caused system wakeup

Add a sysfs attribute, /sys/power/pm_wakeup_irq, reporting the IRQ
number of the first wakeup interrupt (that is, the first interrupt
from an IRQ line armed for system wakeup) seen by the kernel during
the most recent system suspend/resume cycle.

This feature will be useful for system wakeup diagnostics of
spurious wakeup interrupts.

Signed-off-by: Alexandra Yates <[e-mail]>
[ rjw: Fixed up pm_wakeup_irq definition ]
Signed-off-by: Rafael J. Wysocki <[e-mail]>

Documentation/ABI/testing/sysfs-power

···
 		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.
+
+What:		/sys/power/pm_wakeup_irq
+Date:		April 2015
+Contact:	Alexandra Yates <[e-mail]>
+Description:
+		The /sys/power/pm_wakeup_irq file reports to user space the IRQ
+		number of the first wakeup interrupt (that is, the first
+		interrupt from an IRQ line armed for system wakeup) seen by the
+		kernel during the most recent system suspend/resume cycle.
+
+		This output is useful for system wakeup diagnostics of spurious
+		wakeup interrupts.

drivers/base/power/wakeup.c

···
  */
 bool events_check_enabled __read_mostly;
 
+/* First wakeup IRQ seen by the kernel in the last cycle. */
+unsigned int pm_wakeup_irq __read_mostly;
+
 /* If set and the system is suspending, terminate the suspend. */
 static bool pm_abort_suspend __read_mostly;
 
···
 void pm_wakeup_clear(void)
 {
 	pm_abort_suspend = false;
+	pm_wakeup_irq = 0;
+}
+
+void pm_system_irq_wakeup(unsigned int irq_number)
+{
+	if (pm_wakeup_irq == 0) {
+		pm_wakeup_irq = irq_number;
+		pm_system_wakeup();
+	}
 }
 
 /**

include/linux/suspend.h

···
 
 /* drivers/base/power/wakeup.c */
 extern bool events_check_enabled;
+extern unsigned int pm_wakeup_irq;
 
 extern bool pm_wakeup_pending(void);
 extern void pm_system_wakeup(void);
 extern void pm_wakeup_clear(void);
+extern void pm_system_irq_wakeup(unsigned int irq_number);
 extern bool pm_get_wakeup_count(unsigned int *count, bool block);
 extern bool pm_save_wakeup_count(unsigned int count);
 extern void pm_wakep_autosleep_enabled(bool set);
···
 static inline bool pm_wakeup_pending(void) { return false; }
 static inline void pm_system_wakeup(void) {}
 static inline void pm_wakeup_clear(void) {}
+static inline void pm_system_irq_wakeup(unsigned int irq_number) {}
 
 static inline void lock_system_sleep(void) {}
 static inline void unlock_system_sleep(void) {}

kernel/irq/pm.c

···
 		desc->istate |= IRQS_SUSPENDED | IRQS_PENDING;
 		desc->depth++;
 		irq_disable(desc);
-		pm_system_wakeup();
+		pm_system_irq_wakeup(irq_desc_get_irq(desc));
 		return true;
 	}
 	return false;

kernel/power/main.c

···
 {
 	pm_print_times_enabled = !!initcall_debug;
 }
+
+static ssize_t pm_wakeup_irq_show(struct kobject *kobj,
+					struct kobj_attribute *attr,
+					char *buf)
+{
+	return pm_wakeup_irq ? sprintf(buf, "%u\n", pm_wakeup_irq) : -ENODATA;
+}
+
+static ssize_t pm_wakeup_irq_store(struct kobject *kobj,
+					struct kobj_attribute *attr,
+					const char *buf, size_t n)
+{
+	return -EINVAL;
+}
+power_attr(pm_wakeup_irq);
+
 #else /* !CONFIG_PM_SLEEP_DEBUG */
 static inline void pm_print_times_init(void) {}
 #endif /* CONFIG_PM_SLEEP_DEBUG */
···
 #endif
 #ifdef CONFIG_PM_SLEEP_DEBUG
 	&pm_print_times_attr.attr,
+	&pm_wakeup_irq_attr.attr,
 #endif
 #endif
 #ifdef CONFIG_FREEZER