irqdomain: Make normal and nomap irqdomains exclusive

Direct mappings are completely exclusive of normal mappings, meaning
that we can refactor the code slightly so that we can get rid of
the revmap_direct_max_irq field and use the revmap_size field
instead, reducing the size of the irqdomain structure.

Signed-off-by: Marc Zyngier <maz@kernel.org>

include/linux/irqdomain.h

@@ -149,8 +149,6 @@ struct irq_domain_chip_generic;
  * @parent: Pointer to parent irq_domain to support hierarchy irq_domains
  *
  * Revmap data, used internally by irq_domain
- * @revmap_direct_max_irq: The largest hwirq that can be set for controllers that
- *                         support direct mapping
  * @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
@@ -173,7 +171,6 @@ struct irq_domain {
 
 	/* reverse map data. The linear map gets appended to the irq_domain */
 	irq_hw_number_t hwirq_max;
-	unsigned int revmap_direct_max_irq;
 	unsigned int revmap_size;
 	struct radix_tree_root revmap_tree;
 	struct mutex revmap_tree_mutex;
@@ -207,6 +204,9 @@ enum {
 	 */
 	IRQ_DOMAIN_MSI_NOMASK_QUIRK	= (1 << 6),
 
+	/* Irq domain doesn't translate anything */
+	IRQ_DOMAIN_FLAG_NO_MAP		= (1 << 7),
+
 	/*
 	 * Flags starting from IRQ_DOMAIN_FLAG_NONCORE are reserved
 	 * for implementation specific purposes and ignored by the

kernel/irq/irqdomain.c

@@ -146,6 +146,10 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, int size,
 
 	static atomic_t unknown_domains;
 
+	if (WARN_ON((size && direct_max) ||
+		    (!IS_ENABLED(CONFIG_IRQ_DOMAIN_NOMAP) && direct_max)))
+		return NULL;
+
 	domain = kzalloc_node(sizeof(*domain) + (sizeof(unsigned int) * size),
 			      GFP_KERNEL, of_node_to_nid(to_of_node(fwnode)));
 	if (!domain)
@@ -213,8 +217,14 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, int size,
 	domain->ops = ops;
 	domain->host_data = host_data;
 	domain->hwirq_max = hwirq_max;
+
+	if (direct_max) {
+		size = direct_max;
+		domain->flags |= IRQ_DOMAIN_FLAG_NO_MAP;
+	}
+
 	domain->revmap_size = size;
-	domain->revmap_direct_max_irq = direct_max;
+
 	irq_domain_check_hierarchy(domain);
 
 	mutex_lock(&irq_domain_mutex);
@@ -482,9 +492,18 @@ struct irq_domain *irq_get_default_host(void)
 	return irq_default_domain;
 }
 
+static bool irq_domain_is_nomap(struct irq_domain *domain)
+{
+	return IS_ENABLED(CONFIG_IRQ_DOMAIN_NOMAP) &&
+	       (domain->flags & IRQ_DOMAIN_FLAG_NO_MAP);
+}
+
 static void irq_domain_clear_mapping(struct irq_domain *domain,
 				     irq_hw_number_t hwirq)
 {
+	if (irq_domain_is_nomap(domain))
+		return;
+
 	if (hwirq < domain->revmap_size) {
 		domain->revmap[hwirq] = 0;
 	} else {
@@ -498,6 +517,9 @@ static void irq_domain_set_mapping(struct irq_domain *domain,
 				   irq_hw_number_t hwirq,
 				   struct irq_data *irq_data)
 {
+	if (irq_domain_is_nomap(domain))
+		return;
+
 	if (hwirq < domain->revmap_size) {
 		domain->revmap[hwirq] = irq_data->irq;
 	} else {
@@ -629,9 +651,9 @@ unsigned int irq_create_direct_mapping(struct irq_domain *domain)
 		pr_debug("create_direct virq allocation failed\n");
 		return 0;
 	}
-	if (virq >= domain->revmap_direct_max_irq) {
+	if (virq >= domain->revmap_size) {
 		pr_err("ERROR: no free irqs available below %i maximum\n",
-			domain->revmap_direct_max_irq);
+			domain->revmap_size);
 		irq_free_desc(virq);
 		return 0;
 	}
@@ -879,10 +901,14 @@ unsigned int irq_find_mapping(struct irq_domain *domain,
 	if (domain == NULL)
 		return 0;
 
-	if (hwirq < domain->revmap_direct_max_irq) {
-		data = irq_domain_get_irq_data(domain, hwirq);
-		if (data && data->hwirq == hwirq)
-			return hwirq;
+	if (irq_domain_is_nomap(domain)) {
+		if (hwirq < domain->revmap_size) {
+			data = irq_domain_get_irq_data(domain, hwirq);
+			if (data && data->hwirq == hwirq)
+				return hwirq;
+		}
+
+		return 0;
 	}
 
 	/* Check if the hwirq is in the linear revmap. */
@@ -1470,7 +1496,7 @@ static void irq_domain_fix_revmap(struct irq_data *d)
 {
 	void __rcu **slot;
 
-	if (d->hwirq < d->domain->revmap_size)
+	if (irq_domain_is_nomap(d->domain) || d->hwirq < d->domain->revmap_size)
 		return; /* Not using radix tree. */
 
 	/* Fix up the revmap. */
@@ -1830,8 +1856,7 @@ static void
 irq_domain_debug_show_one(struct seq_file *m, struct irq_domain *d, int ind)
 {
 	seq_printf(m, "%*sname:   %s\n", ind, "", d->name);
-	seq_printf(m, "%*ssize:   %u\n", ind + 1, "",
-		   d->revmap_size + d->revmap_direct_max_irq);
+	seq_printf(m, "%*ssize:   %u\n", ind + 1, "", d->revmap_size);
 	seq_printf(m, "%*smapped: %u\n", ind + 1, "", d->mapcount);
 	seq_printf(m, "%*sflags:  0x%08x\n", ind +1 , "", d->flags);
 	if (d->ops && d->ops->debug_show)