m68knommu: support the external GPIO based interrupts of the 5272

The external GPIO interrupts of the ColdFire 5272 SoC are edge triggered,
unlike the internal interrupt sources (which are level triggered).

Add proper support for these interrupts.
Signed-off-by: Greg Ungerer <gerg@uclinux.org>

arch/m68knommu/platform/5272/intc.c

@@ -12,6 +12,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
 #include <linux/irq.h>
 #include <linux/io.h>
 #include <asm/coldfire.h>
@@ -29,6 +30,10 @@
  * via a set of 4 "Interrupt Controller Registers" (ICR). There is a
  * loose mapping of vector number to register and internal bits, but
  * a table is the easiest and quickest way to map them.
+ *
+ * Note that the external interrupts are edge triggered (unlike the
+ * internal interrupt sources which are level triggered). Which means
+ * they also need acknowledgeing via acknowledge bits.
  */
 struct irqmap {
 	unsigned char	icr;
@@ -68,6 +73,11 @@ static struct irqmap intc_irqmap[MCFINT_VECMAX - MCFINT_VECBASE] = {
 	/*MCF_IRQ_SWTO*/	{ .icr = MCFSIM_ICR4, .index = 16, .ack = 0, },
 };
 
+/*
+ * The act of masking the interrupt also has a side effect of 'ack'ing
+ * an interrupt on this irq (for the external irqs). So this mask function
+ * is also an ack_mask function.
+ */
 static void intc_irq_mask(unsigned int irq)
 {
 	if ((irq >= MCFINT_VECBASE) && (irq <= MCFINT_VECMAX)) {
@@ -95,7 +105,9 @@ static void intc_irq_ack(unsigned int irq)
 		irq -= MCFINT_VECBASE;
 		if (intc_irqmap[irq].ack) {
 			u32 v;
-			v = 0xd << intc_irqmap[irq].index;
+			v = readl(MCF_MBAR + intc_irqmap[irq].icr);
+			v &= (0x7 << intc_irqmap[irq].index);
+			v |= (0x8 << intc_irqmap[irq].index);
 			writel(v, MCF_MBAR + intc_irqmap[irq].icr);
 		}
 	}
@@ -103,21 +115,47 @@ static void intc_irq_ack(unsigned int irq)
 
 static int intc_irq_set_type(unsigned int irq, unsigned int type)
 {
-	/* We can set the edge type here for external interrupts */
+	if ((irq >= MCFINT_VECBASE) && (irq <= MCFINT_VECMAX)) {
+		irq -= MCFINT_VECBASE;
+		if (intc_irqmap[irq].ack) {
+			u32 v;
+			v = readl(MCF_MBAR + MCFSIM_PITR);
+			if (type == IRQ_TYPE_EDGE_FALLING)
+				v &= ~(0x1 << (32 - irq));
+			else
+				v |= (0x1 << (32 - irq));
+			writel(v, MCF_MBAR + MCFSIM_PITR);
+		}
+	}
 	return 0;
 }
 
+/*
+ * Simple flow handler to deal with the external edge triggered interrupts.
+ * We need to be careful with the masking/acking due to the side effects
+ * of masking an interrupt.
+ */
+static void intc_external_irq(unsigned int irq, struct irq_desc *desc)
+{
+	kstat_incr_irqs_this_cpu(irq, desc);
+	desc->status |= IRQ_INPROGRESS;
+	desc->chip->ack(irq);
+	handle_IRQ_event(irq, desc->action);
+	desc->status &= ~IRQ_INPROGRESS;
+}
+
 static struct irq_chip intc_irq_chip = {
 	.name		= "CF-INTC",
 	.mask		= intc_irq_mask,
 	.unmask		= intc_irq_unmask,
+	.mask_ack	= intc_irq_mask,
 	.ack		= intc_irq_ack,
 	.set_type	= intc_irq_set_type,
 };
 
 void __init init_IRQ(void)
 {
-	int irq;
+	int irq, edge;
 
 	init_vectors();
 
@@ -129,8 +167,16 @@ void __init init_IRQ(void)
 
 	for (irq = 0; (irq < NR_IRQS); irq++) {
 		set_irq_chip(irq, &intc_irq_chip);
-		set_irq_type(irq, IRQ_TYPE_LEVEL_HIGH);
-		set_irq_handler(irq, handle_level_irq);
+		edge = 0;
+		if ((irq >= MCFINT_VECBASE) && (irq <= MCFINT_VECMAX))
+			edge = intc_irqmap[irq - MCFINT_VECBASE].ack;
+		if (edge) {
+			set_irq_type(irq, IRQ_TYPE_EDGE_RISING);
+			set_irq_handler(irq, intc_external_irq);
+		} else {
+			set_irq_type(irq, IRQ_TYPE_LEVEL_HIGH);
+			set_irq_handler(irq, handle_level_irq);
+		}
 	}
 }