1 files changed, 64 insertions, 2 deletions

diff --git a/arch/powerpc/sysdev/uic.c b/arch/powerpc/sysdev/uic.c
index 89059895a20..47180b3fca5 100644
--- a/arch/powerpc/sysdev/uic.c
+++ b/arch/powerpc/sysdev/uic.c
@@ -24,6 +24,7 @@
 #include <linux/spinlock.h>
 #include <linux/irq.h>
 #include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
 #include <asm/irq.h>
 #include <asm/io.h>
 #include <asm/prom.h>
@@ -142,7 +143,7 @@ static int uic_set_irq_type(unsigned int virq, unsigned int flow_type)
 
 	desc->status &= ~(IRQ_TYPE_SENSE_MASK | IRQ_LEVEL);
 	desc->status |= flow_type & IRQ_TYPE_SENSE_MASK;
-	if (trigger)
+	if (!trigger)
 		desc->status |= IRQ_LEVEL;
 
 	spin_unlock_irqrestore(&uic->lock, flags);
@@ -159,6 +160,64 @@ static struct irq_chip uic_irq_chip = {
 	.set_type	= uic_set_irq_type,
 };
 
+/**
+ *	handle_uic_irq - irq flow handler for UIC
+ *	@irq:	the interrupt number
+ *	@desc:	the interrupt description structure for this irq
+ *
+ * This is modified version of the generic handle_level_irq() suitable
+ * for the UIC.  On the UIC, acking (i.e. clearing the SR bit) a level
+ * irq will have no effect if the interrupt is still asserted by the
+ * device, even if the interrupt is already masked.  Therefore, unlike
+ * the standard handle_level_irq(), we must ack the interrupt *after*
+ * invoking the ISR (which should have de-asserted the interrupt in
+ * the external source).  For edge interrupts we ack at the beginning
+ * instead of the end, to keep the window in which we can miss an
+ * interrupt as small as possible.
+ */
+void fastcall handle_uic_irq(unsigned int irq, struct irq_desc *desc)
+{
+	unsigned int cpu = smp_processor_id();
+	struct irqaction *action;
+	irqreturn_t action_ret;
+
+	spin_lock(&desc->lock);
+	if (desc->status & IRQ_LEVEL)
+		desc->chip->mask(irq);
+	else
+		desc->chip->mask_ack(irq);
+
+	if (unlikely(desc->status & IRQ_INPROGRESS))
+		goto out_unlock;
+	desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
+	kstat_cpu(cpu).irqs[irq]++;
+
+	/*
+	 * If its disabled or no action available
+	 * keep it masked and get out of here
+	 */
+	action = desc->action;
+	if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
+		desc->status |= IRQ_PENDING;
+		goto out_unlock;
+	}
+
+	desc->status |= IRQ_INPROGRESS;
+	desc->status &= ~IRQ_PENDING;
+	spin_unlock(&desc->lock);
+
+	action_ret = handle_IRQ_event(irq, action);
+
+	spin_lock(&desc->lock);
+	desc->status &= ~IRQ_INPROGRESS;
+	if (desc->status & IRQ_LEVEL)
+		desc->chip->ack(irq);
+	if (!(desc->status & IRQ_DISABLED) && desc->chip->unmask)
+		desc->chip->unmask(irq);
+out_unlock:
+	spin_unlock(&desc->lock);
+}
+
 static int uic_host_match(struct irq_host *h, struct device_node *node)
 {
 	struct uic *uic = h->host_data;
@@ -173,7 +232,7 @@ static int uic_host_map(struct irq_host *h, unsigned int virq,
 	set_irq_chip_data(virq, uic);
 	/* Despite the name, handle_level_irq() works for both level
 	 * and edge irqs on UIC.  FIXME: check this is correct */
-	set_irq_chip_and_handler(virq, &uic_irq_chip, handle_level_irq);
+	set_irq_chip_and_handler(virq, &uic_irq_chip, handle_uic_irq);
 
 	/* Set default irq type */
 	set_irq_type(virq, IRQ_TYPE_NONE);
@@ -207,6 +266,9 @@ irqreturn_t uic_cascade(int virq, void *data)
 	int subvirq;
 
 	msr = mfdcr(uic->dcrbase + UIC_MSR);
+	if (!msr) /* spurious interrupt */
+		return IRQ_HANDLED;
+
 	src = 32 - ffs(msr);
 
 	subvirq = irq_linear_revmap(uic->irqhost, src);