PCI: irq: Introduce rearm_wake_irq()

Introduce a new function, rearm_wake_irq(), allowing a wakeup IRQ
to be armed for systen wakeup detection again without running any
action handlers associated with it after it has been armed for
wakeup detection and triggered.

That is useful for IRQs, like ACPI SCI, that may deliver wakeup
as well as non-wakeup interrupts when armed for systen wakeup
detection.  In those cases, it may be possible to determine whether
or not the delivered interrupt is a systen wakeup one without
running the entire action handler (or handlers, if the IRQ is
shared) for the IRQ, and if the interrupt turns out to be a
non-wakeup one, the IRQ can be rearmed with the help of the
new function.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/interrupt.h

@@ -238,6 +238,7 @@ extern void teardown_percpu_nmi(unsigned int irq);
 /* The following three functions are for the core kernel use only. */
 extern void suspend_device_irqs(void);
 extern void resume_device_irqs(void);
+extern void rearm_wake_irq(unsigned int irq);
 
 /**
  * struct irq_affinity_notify - context for notification of IRQ affinity changes

kernel/irq/pm.c

@@ -176,6 +176,26 @@ static void resume_irqs(bool want_early)
 	}
 }
 
+/**
+ * rearm_wake_irq - rearm a wakeup interrupt line after signaling wakeup
+ * @irq: Interrupt to rearm
+ */
+void rearm_wake_irq(unsigned int irq)
+{
+	unsigned long flags;
+	struct irq_desc *desc = irq_get_desc_buslock(irq, &flags, IRQ_GET_DESC_CHECK_GLOBAL);
+
+	if (!desc || !(desc->istate & IRQS_SUSPENDED) ||
+	    !irqd_is_wakeup_set(&desc->irq_data))
+		return;
+
+	desc->istate &= ~IRQS_SUSPENDED;
+	irqd_set(&desc->irq_data, IRQD_WAKEUP_ARMED);
+	__enable_irq(desc);
+
+	irq_put_desc_busunlock(desc, flags);
+}
+
 /**
  * irq_pm_syscore_ops - enable interrupt lines early
  *