sh: intc: Handle early lookups of subgroup IRQs.

If lookups happen while the radix node still points to a subgroup
mapping, an IRQ hasn't yet been made available for the specified id, so
error out accordingly. Once the slot is replaced with an IRQ mapping and
the tag is discarded, lookup can commence as normal.

Signed-off-by: Paul Mundt <[e-mail]>

drivers/sh/intc.c

···
 	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;
 		}
 	}
 
···
 	return _INTC_MK(fn, MODE_ENABLE_REG, intc_get_reg(d, subgroup->reg),
 			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,

include/linux/sh_intc.h

···
 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