Index: linux-2.6.30.5/arch/mips/kernel/traps.c
===================================================================
--- linux-2.6.30.5.orig/arch/mips/kernel/traps.c	2009-08-16 23:19:38.000000000 +0200
+++ linux-2.6.30.5/arch/mips/kernel/traps.c	2009-09-02 18:23:37.000000000 +0200
@@ -1542,7 +1542,16 @@
 	 */
 	if (cpu_has_mips_r2) {
 		cp0_compare_irq = (read_c0_intctl() >> 29) & 7;
+		if (!cp0_compare_irq)
+			cp0_compare_irq = CP0_LEGACY_COMPARE_IRQ;
+
 		cp0_perfcount_irq = (read_c0_intctl() >> 26) & 7;
+		if (!cp0_perfcount_irq)
+			cp0_perfcount_irq = CP0_LEGACY_PERFCNT_IRQ;
+
+		if (arch_fixup_c0_irqs)
+			arch_fixup_c0_irqs();
+
 		if (cp0_perfcount_irq == cp0_compare_irq)
 			cp0_perfcount_irq = -1;
 	} else {
Index: linux-2.6.30.5/arch/mips/include/asm/irq.h
===================================================================
--- linux-2.6.30.5.orig/arch/mips/include/asm/irq.h	2009-09-02 18:24:49.000000000 +0200
+++ linux-2.6.30.5/arch/mips/include/asm/irq.h	2009-09-02 18:26:05.000000000 +0200
@@ -157,8 +157,10 @@
  * IE7.  Since R2 their number has to be read from the c0_intctl register.
  */
 #define CP0_LEGACY_COMPARE_IRQ 7
+#define CP0_LEGACY_PERFCNT_IRQ 7
 
 extern int cp0_compare_irq;
 extern int cp0_perfcount_irq;
+extern void __weak arch_fixup_c0_irqs(void);
 
 #endif /* _ASM_IRQ_H */