irqdomain: Cache irq_data instead of a virq number in the revmap

Caching a virq number in the revmap is pretty inefficient, as
it means we will need to convert it back to either an irq_data
or irq_desc to do anything with it.

It is also a bit odd, as the radix tree does cache irq_data
pointers.

Change the revmap type to be an irq_data pointer instead of
an unsigned int, and preserve the current API for now.
Signed-off-by: Marc Zyngier <maz@kernel.org>

include/linux/irqdomain.h

@@ -151,7 +151,7 @@ struct irq_domain_chip_generic;
  * Revmap data, used internally by irq_domain
  * @revmap_size: Size of the linear map table @revmap[]
  * @revmap_tree: Radix map tree for hwirqs that don't fit in the linear map
- * @revmap: Linear table of hwirq->virq reverse mappings
+ * @revmap: Linear table of irq_data pointers
  */
 struct irq_domain {
 	struct list_head link;
@@ -174,7 +174,7 @@ struct irq_domain {
 	unsigned int revmap_size;
 	struct radix_tree_root revmap_tree;
 	struct mutex revmap_tree_mutex;
-	unsigned int revmap[];
+	struct irq_data *revmap[];
 };
 
 /* Irq domain flags */

kernel/irq/irqdomain.c

@@ -505,7 +505,7 @@ static void irq_domain_clear_mapping(struct irq_domain *domain,
 		return;
 
 	if (hwirq < domain->revmap_size) {
-		domain->revmap[hwirq] = 0;
+		domain->revmap[hwirq] = NULL;
 	} else {
 		mutex_lock(&domain->revmap_tree_mutex);
 		radix_tree_delete(&domain->revmap_tree, hwirq);
@@ -521,7 +521,7 @@ static void irq_domain_set_mapping(struct irq_domain *domain,
 		return;
 
 	if (hwirq < domain->revmap_size) {
-		domain->revmap[hwirq] = irq_data->irq;
+		domain->revmap[hwirq] = irq_data;
 	} else {
 		mutex_lock(&domain->revmap_tree_mutex);
 		radix_tree_insert(&domain->revmap_tree, hwirq, irq_data);
@@ -913,7 +913,7 @@ unsigned int irq_find_mapping(struct irq_domain *domain,
 
 	/* Check if the hwirq is in the linear revmap. */
 	if (hwirq < domain->revmap_size)
-		return domain->revmap[hwirq];
+		return domain->revmap[hwirq]->irq;
 
 	rcu_read_lock();
 	data = radix_tree_lookup(&domain->revmap_tree, hwirq);
@@ -1496,8 +1496,14 @@ static void irq_domain_fix_revmap(struct irq_data *d)
 {
 	void __rcu **slot;
 
-	if (irq_domain_is_nomap(d->domain) || d->hwirq < d->domain->revmap_size)
-		return; /* Not using radix tree. */
+	if (irq_domain_is_nomap(d->domain))
+		return;
+
+	if (d->hwirq < d->domain->revmap_size) {
+		/* Not using radix tree */
+		d->domain->revmap[d->hwirq] = d;
+		return;
+	}
 
 	/* Fix up the revmap. */
 	mutex_lock(&d->domain->revmap_tree_mutex);