genirq/msi: Allow creation of a tree-based irqdomain for platform-msi

platform_msi_create_device_domain() always creates a revmap-based
irqdomain, which has the drawback of requiring the number of MSIs
that can be allocated ahead of time. This is not always possible,
and we sometimes need to use a tree-based irqdomain instead.

Add a new platform_msi_create_device_tree_domain() helper to
that effect.
Reported-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/base/platform-msi.c

@@ -321,8 +321,9 @@ void *platform_msi_get_host_data(struct irq_domain *domain)
  * Returns an irqdomain for @nvec interrupts
  */
 struct irq_domain *
-platform_msi_create_device_domain(struct device *dev,
+__platform_msi_create_device_domain(struct device *dev,
 				    unsigned int nvec,
+				    bool is_tree,
 				    irq_write_msi_msg_t write_msi_msg,
 				    const struct irq_domain_ops *ops,
 				    void *host_data)
@@ -336,7 +337,8 @@ platform_msi_create_device_domain(struct device *dev,
 		return NULL;
 
 	data->host_data = host_data;
-	domain = irq_domain_create_hierarchy(dev->msi_domain, 0, nvec,
+	domain = irq_domain_create_hierarchy(dev->msi_domain, 0,
+					     is_tree ? 0 : nvec,
 					     dev->fwnode, ops, data);
 	if (!domain)
 		goto free_priv;

include/linux/msi.h

@@ -317,11 +317,18 @@ int msi_domain_prepare_irqs(struct irq_domain *domain, struct device *dev,
 int msi_domain_populate_irqs(struct irq_domain *domain, struct device *dev,
 			     int virq, int nvec, msi_alloc_info_t *args);
 struct irq_domain *
-platform_msi_create_device_domain(struct device *dev,
+__platform_msi_create_device_domain(struct device *dev,
 				    unsigned int nvec,
+				    bool is_tree,
 				    irq_write_msi_msg_t write_msi_msg,
 				    const struct irq_domain_ops *ops,
 				    void *host_data);
+
+#define platform_msi_create_device_domain(dev, nvec, write, ops, data)	\
+	__platform_msi_create_device_domain(dev, nvec, false, write, ops, data)
+#define platform_msi_create_device_tree_domain(dev, nvec, write, ops, data) \
+	__platform_msi_create_device_domain(dev, nvec, true, write, ops, data)
+
 int platform_msi_domain_alloc(struct irq_domain *domain, unsigned int virq,
 			      unsigned int nr_irqs);
 void platform_msi_domain_free(struct irq_domain *domain, unsigned int virq,