x86/hpet: Cure interface abuse in the resume path

The HPET resume path abuses irq_domain_[de]activate_irq() to restore the
MSI message in the HPET chip for the boot CPU on resume and it relies on an
implementation detail of the interrupt core code, which magically makes the
HPET unmask call invoked via a irq_disable/enable pair. This worked as long
as the irq code did unconditionally invoke the unmask() callback. With the
recent changes which keep track of the masked state to avoid expensive
hardware access, this does not longer work. As a consequence the HPET timer
interrupts are not unmasked which breaks resume as the boot CPU waits
forever that a timer interrupt arrives.

Make the restore of the MSI message explicit and invoke the unmask()
function directly. While at it get rid of the pointless affinity setting as
nothing can change the affinity of the interrupt and the vector across
suspend/resume. The restore of the MSI message reestablishes the previous
affinity setting which is the correct one.

Fixes: bf22ff45 ("genirq: Avoid unnecessary low level irq function calls")
Reported-and-tested-by: Tomi Sarvela <tomi.p.sarvela@intel.com>
Reported-by: Martin Peres <martin.peres@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: jeffy.chen@rock-chips.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1707312158590.2287@nanos

arch/x86/kernel/hpet.c

@@ -345,21 +345,10 @@ static int hpet_shutdown(struct clock_event_device *evt, int timer)
 	return 0;
 }
 
-static int hpet_resume(struct clock_event_device *evt, int timer)
-{
-	if (!timer) {
-		hpet_enable_legacy_int();
-	} else {
-		struct hpet_dev *hdev = EVT_TO_HPET_DEV(evt);
-
-		irq_domain_deactivate_irq(irq_get_irq_data(hdev->irq));
-		irq_domain_activate_irq(irq_get_irq_data(hdev->irq));
-		disable_hardirq(hdev->irq);
-		irq_set_affinity(hdev->irq, cpumask_of(hdev->cpu));
-		enable_irq(hdev->irq);
-	}
+static int hpet_resume(struct clock_event_device *evt)
+{
+	hpet_enable_legacy_int();
 	hpet_print_config();
-
 	return 0;
 }
 
@@ -417,7 +406,7 @@ static int hpet_legacy_set_periodic(struct clock_event_device *evt)
 
 static int hpet_legacy_resume(struct clock_event_device *evt)
 {
-	return hpet_resume(evt, 0);
+	return hpet_resume(evt);
 }
 
 static int hpet_legacy_next_event(unsigned long delta,
@@ -510,8 +499,14 @@ static int hpet_msi_set_periodic(struct clock_event_device *evt)
 static int hpet_msi_resume(struct clock_event_device *evt)
 {
 	struct hpet_dev *hdev = EVT_TO_HPET_DEV(evt);
+	struct irq_data *data = irq_get_irq_data(hdev->irq);
+	struct msi_msg msg;
 
-	return hpet_resume(evt, hdev->num);
+	/* Restore the MSI msg and unmask the interrupt */
+	irq_chip_compose_msi_msg(data, &msg);
+	hpet_msi_write(hdev, &msg);
+	hpet_msi_unmask(data);
+	return 0;
 }
 
 static int hpet_msi_next_event(unsigned long delta,