Optimise reading of pending interrupt registers. If there are no

pending interrupt bits, skip the bit iteration loop.

Reviewed by:	ian @

1 files changed, 27 insertions, 19 deletions

diff --git a/sys/arm/broadcom/bcm2835/bcm2835_intr.c b/sys/arm/broadcom/bcm2835/bcm2835_intr.c
index 4a94c69..7a06eb0 100644
--- a/sys/arm/broadcom/bcm2835/bcm2835_intr.c
+++ b/sys/arm/broadcom/bcm2835/bcm2835_intr.c
@@ -60,6 +60,7 @@ __FBSDID("$FreeBSD$");
 #define	BANK1_END	(BANK1_START + 32 - 1)
 #define	BANK2_START	(BANK1_START + 32)
 #define	BANK2_END	(BANK2_START + 32 - 1)
+#define	BANK3_START	(BANK2_START + 32)
 
 #define	IS_IRQ_BASIC(n)	(((n) >= 0) && ((n) < BANK1_START))
 #define	IS_IRQ_BANK1(n)	(((n) >= BANK1_START) && ((n) <= BANK1_END))
@@ -150,29 +151,36 @@ arm_get_next_irq(int last_irq)
 	/* Sanity check */
 	if (irq < 0)
 		irq = 0;
-	
+
 	/* TODO: should we mask last_irq? */
-	pending = intc_read_4(INTC_PENDING_BASIC);
-	while (irq < BANK1_START) {
-		if (pending & (1 << irq))
-			return irq;
-		irq++;
+	if (irq < BANK1_START) {
+		pending = intc_read_4(INTC_PENDING_BASIC);
+		if ((pending & 0xFF) == 0) {
+			irq  = BANK1_START;	/* skip to next bank */
+		} else do {
+			if (pending & (1 << irq))
+				return irq;
+			irq++;
+		} while (irq < BANK1_START);
 	}
-
-	pending = intc_read_4(INTC_PENDING_BANK1);
-	while (irq < BANK2_START) {
-		if (pending & (1 << IRQ_BANK1(irq)))
-			return irq;
-		irq++;
+	if (irq < BANK2_START) {
+		pending = intc_read_4(INTC_PENDING_BANK1);
+		if (pending == 0) {
+			irq  = BANK2_START;	/* skip to next bank */
+		} else do {
+			if (pending & (1 << IRQ_BANK1(irq)))
+				return irq;
+			irq++;
+		} while (irq < BANK2_START);
 	}
-
-	pending = intc_read_4(INTC_PENDING_BANK2);
-	while (irq <= BANK2_END) {
-		if (pending & (1 << IRQ_BANK2(irq)))
-			return irq;
-		irq++;
+	if (irq < BANK3_START) {
+		pending = intc_read_4(INTC_PENDING_BANK2);
+		if (pending != 0) do {
+			if (pending & (1 << IRQ_BANK2(irq)))
+				return irq;
+			irq++;
+		} while (irq < BANK3_START);
 	}
-
 	return (-1);
 }