diff --git a/arch/powerpc/sysdev/mpc8xx_pic.c b/arch/powerpc/sysdev/mpc8xx_pic.c
index d5f5416be310..b724622c3a0b 100644
--- a/arch/powerpc/sysdev/mpc8xx_pic.c
+++ b/arch/powerpc/sysdev/mpc8xx_pic.c
@@ -18,69 +18,45 @@
 extern int cpm_get_irq(struct pt_regs *regs);
 
 static struct irq_domain *mpc8xx_pic_host;
-#define NR_MASK_WORDS   ((NR_IRQS + 31) / 32)
-static unsigned long ppc_cached_irq_mask[NR_MASK_WORDS];
+static unsigned long mpc8xx_cached_irq_mask;
 static sysconf8xx_t __iomem *siu_reg;
 
-int cpm_get_irq(struct pt_regs *regs);
+static inline unsigned long mpc8xx_irqd_to_bit(struct irq_data *d)
+{
+	return 0x80000000 >> irqd_to_hwirq(d);
+}
 
 static void mpc8xx_unmask_irq(struct irq_data *d)
 {
-	int	bit, word;
-	unsigned int irq_nr = (unsigned int)irqd_to_hwirq(d);
-
-	bit = irq_nr & 0x1f;
-	word = irq_nr >> 5;
-
-	ppc_cached_irq_mask[word] |= (1 << (31-bit));
-	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask[word]);
+	mpc8xx_cached_irq_mask |= mpc8xx_irqd_to_bit(d);
+	out_be32(&siu_reg->sc_simask, mpc8xx_cached_irq_mask);
 }
 
 static void mpc8xx_mask_irq(struct irq_data *d)
 {
-	int	bit, word;
-	unsigned int irq_nr = (unsigned int)irqd_to_hwirq(d);
-
-	bit = irq_nr & 0x1f;
-	word = irq_nr >> 5;
-
-	ppc_cached_irq_mask[word] &= ~(1 << (31-bit));
-	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask[word]);
+	mpc8xx_cached_irq_mask &= ~mpc8xx_irqd_to_bit(d);
+	out_be32(&siu_reg->sc_simask, mpc8xx_cached_irq_mask);
 }
 
 static void mpc8xx_ack(struct irq_data *d)
 {
-	int	bit;
-	unsigned int irq_nr = (unsigned int)irqd_to_hwirq(d);
-
-	bit = irq_nr & 0x1f;
-	out_be32(&siu_reg->sc_sipend, 1 << (31-bit));
+	out_be32(&siu_reg->sc_sipend, mpc8xx_irqd_to_bit(d));
 }
 
 static void mpc8xx_end_irq(struct irq_data *d)
 {
-	int bit, word;
-	unsigned int irq_nr = (unsigned int)irqd_to_hwirq(d);
-
-	bit = irq_nr & 0x1f;
-	word = irq_nr >> 5;
-
-	ppc_cached_irq_mask[word] |= (1 << (31-bit));
-	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask[word]);
+	mpc8xx_cached_irq_mask |= mpc8xx_irqd_to_bit(d);
+	out_be32(&siu_reg->sc_simask, mpc8xx_cached_irq_mask);
 }
 
 static int mpc8xx_set_irq_type(struct irq_data *d, unsigned int flow_type)
 {
-	if (flow_type & IRQ_TYPE_EDGE_FALLING) {
-		irq_hw_number_t hw = (unsigned int)irqd_to_hwirq(d);
+	/* only external IRQ senses are programmable */
+	if ((flow_type & IRQ_TYPE_EDGE_FALLING) && !(irqd_to_hwirq(d) & 1)) {
 		unsigned int siel = in_be32(&siu_reg->sc_siel);
-
-		/* only external IRQ senses are programmable */
-		if ((hw & 1) == 0) {
-			siel |= (0x80000000 >> hw);
-			out_be32(&siu_reg->sc_siel, siel);
-			__irq_set_handler_locked(d->irq, handle_edge_irq);
-		}
+		siel |= mpc8xx_irqd_to_bit(d);
+		out_be32(&siu_reg->sc_siel, siel);
+		__irq_set_handler_locked(d->irq, handle_edge_irq);
 	}
 	return 0;
 }
@@ -132,6 +108,9 @@ static int mpc8xx_pic_host_xlate(struct irq_domain *h, struct device_node *ct,
 		IRQ_TYPE_EDGE_FALLING,
 	};
 
+	if (intspec[0] > 0x1f)
+		return 0;
+
 	*out_hwirq = intspec[0];
 	if (intsize > 1 && intspec[1] < 4)
 		*out_flags = map_pic_senses[intspec[1]];