powerpc/opal-irqchip: Fix double endian conversion

The OPAL event calls return a mask of events that are active in big
endian format. This is checked when unmasking the events in the
irqchip by comparison with a cached value. The cached value was stored
in big endian format but should've been converted to CPU endian
first.

This bug leads to OPAL event delivery being delayed or dropped on some
systems. Symptoms may include a non-functional console.

The bug is fixed by calling opal_handle_events(...) instead of
duplicating code in opal_event_unmask(...).

Fixes: 9f0fd0499d30 ("powerpc/powernv: Add a virtual irqchip for opal events")
Cc: stable@vger.kernel.org # v4.2+
Reported-by: Douglas L Lehr <dllehr@us.ibm.com>
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/opal-irqchip.c

@@ -43,11 +43,34 @@ static unsigned int opal_irq_count;
 static unsigned int *opal_irqs;
 
 static void opal_handle_irq_work(struct irq_work *work);
-static __be64 last_outstanding_events;
+static u64 last_outstanding_events;
 static struct irq_work opal_event_irq_work = {
 	.func = opal_handle_irq_work,
 };
 
+void opal_handle_events(uint64_t events)
+{
+	int virq, hwirq = 0;
+	u64 mask = opal_event_irqchip.mask;
+
+	if (!in_irq() && (events & mask)) {
+		last_outstanding_events = events;
+		irq_work_queue(&opal_event_irq_work);
+		return;
+	}
+
+	while (events & mask) {
+		hwirq = fls64(events) - 1;
+		if (BIT_ULL(hwirq) & mask) {
+			virq = irq_find_mapping(opal_event_irqchip.domain,
+						hwirq);
+			if (virq)
+				generic_handle_irq(virq);
+		}
+		events &= ~BIT_ULL(hwirq);
+	}
+}
+
 static void opal_event_mask(struct irq_data *d)
 {
 	clear_bit(d->hwirq, &opal_event_irqchip.mask);
@@ -55,12 +78,12 @@ static void opal_event_mask(struct irq_data *d)
 
 static void opal_event_unmask(struct irq_data *d)
 {
+	__be64 events;
+
 	set_bit(d->hwirq, &opal_event_irqchip.mask);
 
-	opal_poll_events(&last_outstanding_events);
-	if (last_outstanding_events & opal_event_irqchip.mask)
-		/* Need to retrigger the interrupt */
-		irq_work_queue(&opal_event_irq_work);
+	opal_poll_events(&events);
+	opal_handle_events(be64_to_cpu(events));
 }
 
 static int opal_event_set_type(struct irq_data *d, unsigned int flow_type)
@@ -96,29 +119,6 @@ static int opal_event_map(struct irq_domain *d, unsigned int irq,
 	return 0;
 }
 
-void opal_handle_events(uint64_t events)
-{
-	int virq, hwirq = 0;
-	u64 mask = opal_event_irqchip.mask;
-
-	if (!in_irq() && (events & mask)) {
-		last_outstanding_events = events;
-		irq_work_queue(&opal_event_irq_work);
-		return;
-	}
-
-	while (events & mask) {
-		hwirq = fls64(events) - 1;
-		if (BIT_ULL(hwirq) & mask) {
-			virq = irq_find_mapping(opal_event_irqchip.domain,
-						hwirq);
-			if (virq)
-				generic_handle_irq(virq);
-		}
-		events &= ~BIT_ULL(hwirq);
-	}
-}
-
 static irqreturn_t opal_interrupt(int irq, void *data)
 {
 	__be64 events;
@@ -131,7 +131,7 @@ static irqreturn_t opal_interrupt(int irq, void *data)
 
 static void opal_handle_irq_work(struct irq_work *work)
 {
-	opal_handle_events(be64_to_cpu(last_outstanding_events));
+	opal_handle_events(last_outstanding_events);
 }
 
 static int opal_event_match(struct irq_domain *h, struct device_node *node,