Index: linux-2.6.33.2/arch/mips/kernel/traps.c
===================================================================
--- linux-2.6.33.2.orig/arch/mips/kernel/traps.c	2010-04-02 01:02:33.000000000 +0200
+++ linux-2.6.33.2/arch/mips/kernel/traps.c	2010-04-02 23:36:16.000000000 +0200
@@ -1496,7 +1496,18 @@
 	if (cpu_has_mips_r2) {
 		cp0_compare_irq_shift = CAUSEB_TI - CAUSEB_IP;
 		cp0_compare_irq = (read_c0_intctl() >> INTCTLB_IPTI) & 7;
+
+		if (!cp0_compare_irq)
+			cp0_compare_irq = CP0_LEGACY_COMPARE_IRQ;
+
 		cp0_perfcount_irq = (read_c0_intctl() >> INTCTLB_IPPCI) & 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-2.6.33.2/arch/mips/include/asm/irq.h
===================================================================
--- linux-2.6.33.2.orig/arch/mips/include/asm/irq.h	2010-04-02 01:02:33.000000000 +0200
+++ linux-2.6.33.2/arch/mips/include/asm/irq.h	2010-04-02 23:37:14.000000000 +0200
@@ -133,9 +133,11 @@
  * 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_compare_irq_shift;
 extern int cp0_perfcount_irq;
+extern void __weak arch_fixup_c0_irqs(void);
 
 #endif /* _ASM_IRQ_H */