2 files changed, 25 insertions, 11 deletions

diff --git a/drivers/sh/intc.c b/drivers/sh/intc.c
index c81fe23db7f7..d4325c70cf61 100644
--- a/drivers/sh/intc.c
+++ b/drivers/sh/intc.c
@@ -927,19 +927,35 @@ static unsigned int __init intc_sense_data(struct intc_desc *desc,
         return 0;
 }
 
-unsigned int intc_irq_lookup(const char *chipname, intc_enum enum_id)
+#define INTC_TAG_VIRQ_NEEDS_ALLOC       0
+
+int intc_irq_lookup(const char *chipname, intc_enum enum_id)
 {
         struct intc_map_entry *ptr;
         struct intc_desc_int *d;
-        unsigned int irq = 0;
+        int irq = -1;
 
         list_for_each_entry(d, &intc_list, list) {
-                if (strcmp(d->chip.name, chipname) == 0) {
-                        ptr = radix_tree_lookup(&d->tree, enum_id);
-                        if (ptr) {
-                                irq = ptr - intc_irq_xlate;
-                                break;
-                        }
+                int tagged;
+
+                if (strcmp(d->chip.name, chipname) != 0)
+                        continue;
+
+                /*
+                 * Catch early lookups for subgroup VIRQs that have not
+                 * yet been allocated an IRQ. This already includes a
+                 * fast-path out if the tree is untagged, so there is no
+                 * need to explicitly test the root tree.
+                 */
+                tagged = radix_tree_tag_get(&d->tree, enum_id,
+                                            INTC_TAG_VIRQ_NEEDS_ALLOC);
+                if (unlikely(tagged))
+                        break;
+
+                ptr = radix_tree_lookup(&d->tree, enum_id);
+                if (ptr) {
+                        irq = ptr - intc_irq_xlate;
+                        break;
                 }
         }
 
@@ -1003,8 +1019,6 @@ static unsigned long __init intc_subgroup_data(struct intc_subgroup *subgroup,
                         0, 1, (subgroup->reg_width - 1) - index);
 }
 
-#define INTC_TAG_VIRQ_NEEDS_ALLOC       0
-
 static void __init intc_subgroup_init_one(struct intc_desc *desc,
                                           struct intc_desc_int *d,
                                           struct intc_subgroup *subgroup)
diff --git a/include/linux/sh_intc.h b/include/linux/sh_intc.h
index 04134a6c7b52..1fc69701e0f8 100644
--- a/include/linux/sh_intc.h
+++ b/include/linux/sh_intc.h
@@ -117,7 +117,7 @@ struct intc_desc symbol __initdata = {					\
 int __init register_intc_controller(struct intc_desc *desc);
 void reserve_intc_vectors(struct intc_vect *vectors, unsigned int nr_vecs);
 int intc_set_priority(unsigned int irq, unsigned int prio);
-unsigned int intc_irq_lookup(const char *chipname, intc_enum enum_id);
+int intc_irq_lookup(const char *chipname, intc_enum enum_id);
 void intc_finalize(void);
 
 #ifdef CONFIG_INTC_USERIMASK