--- a/arch/powerpc/sysdev/ipic.c	2009-02-18 09:47:04.000000000 +0800
+++ b/arch/powerpc/sysdev/ipic.c	2009-02-18 09:46:34.000000000 +0800
@@ -568,8 +568,7 @@ static void ipic_ack_irq(unsigned int vi

 	spin_lock_irqsave(&ipic_lock, flags);

-	temp = ipic_read(ipic->regs, ipic_info[src].ack);
-	temp |= (1 << (31 - ipic_info[src].bit));
+	temp = 1 << (31 - ipic_info[src].bit);
 	ipic_write(ipic->regs, ipic_info[src].ack, temp);

 	/* mb() can't guarantee that ack is finished.  But it does finish
@@ -592,8 +591,7 @@ static void ipic_mask_irq_and_ack(unsign
 	temp &= ~(1 << (31 - ipic_info[src].bit));
 	ipic_write(ipic->regs, ipic_info[src].mask, temp);

-	temp = ipic_read(ipic->regs, ipic_info[src].ack);
-	temp |= (1 << (31 - ipic_info[src].bit));
+	temp = 1 << (31 - ipic_info[src].bit);
 	ipic_write(ipic->regs, ipic_info[src].ack, temp);

 	/* mb() can't guarantee that ack is finished.  But it does finish