1 files changed, 6 insertions, 2 deletions

diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index b9b989d305dd..16eb743b38a7 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1331,9 +1331,13 @@ struct mpic * __init mpic_alloc(struct device_node *node,
         /*
          * By default, the last source number comes from the MPIC, but the
          * device-tree and board support code can override it on buggy hw.
+         * If we get passed an isu_size (multi-isu MPIC) then we use that
+         * as a default instead of the value read from the HW.
          */
         last_irq = (greg_feature & MPIC_GREG_FEATURE_LAST_SRC_MASK)
-                                >> MPIC_GREG_FEATURE_LAST_SRC_SHIFT;
+                                >> MPIC_GREG_FEATURE_LAST_SRC_SHIFT;    
+        if (isu_size)
+                last_irq = isu_size  * MPIC_MAX_ISU - 1;
         of_property_read_u32(mpic->node, "last-interrupt-source", &last_irq);
         if (irq_count)
                 last_irq = irq_count - 1;
@@ -1352,7 +1356,7 @@ struct mpic * __init mpic_alloc(struct device_node *node,
         mpic->isu_mask = (1 << mpic->isu_shift) - 1;
 
         mpic->irqhost = irq_alloc_host(mpic->node, IRQ_HOST_MAP_LINEAR,
-                                       mpic->isu_size, &mpic_host_ops,
+                                       last_irq + 1, &mpic_host_ops,
                                        intvec_top + 1);
 
         /*