diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 8619f2a..466e218 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1144,9 +1144,12 @@
 	mpic->num_cpus = ((greg_feature & MPIC_GREG_FEATURE_LAST_CPU_MASK)
 			  >> MPIC_GREG_FEATURE_LAST_CPU_SHIFT) + 1;
 	if (isu_size == 0)
-		mpic->num_sources =
-			((greg_feature & MPIC_GREG_FEATURE_LAST_SRC_MASK)
-			 >> MPIC_GREG_FEATURE_LAST_SRC_SHIFT) + 1;
+		if (flags & MPIC_BROKEN_FRR_NIRQS)
+			mpic->num_sources = mpic->irq_count;
+		else
+			mpic->num_sources =
+				((greg_feature & MPIC_GREG_FEATURE_LAST_SRC_MASK)
+				 >> MPIC_GREG_FEATURE_LAST_SRC_SHIFT) + 1;
 
 	/* Map the per-CPU registers */
 	for (i = 0; i < mpic->num_cpus; i++) {