of/irq: introduce of_irq_init

of_irq_init will scan the devicetree for matching interrupt controller
nodes. Then it calls an initialization function for each found controller
in the proper order with parent nodes initialized before child nodes.

Based on initial pseudo code from Grant Likely.

Changes in v4:
- Drop unnecessary empty list check
- Be more verbose on errors
- Simplify "if (!desc) WARN_ON(1)" to "if (WARN_ON(!desc))"

Changes in v3:
- add missing kfree's found by Jamie
- Implement Grant's comments to simplify the init loop
- fix function comments

Changes in v2:
- Complete re-write of list searching code from Grant Likely
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Reviewed-by: Jamie Iles <jamie@jamieiles.com>
Tested-by: Thomas Abraham <thomas.abraham@linaro.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>

drivers/of/irq.c

@@ -19,10 +19,12 @@
  */
 
 #include <linux/errno.h>
+#include <linux/list.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/string.h>
+#include <linux/slab.h>
 
 /* For archs that don't support NO_IRQ (such as x86), provide a dummy value */
 #ifndef NO_IRQ
@@ -386,3 +388,108 @@ int of_irq_to_resource_table(struct device_node *dev, struct resource *res,
 
 	return i;
 }
+
+struct intc_desc {
+	struct list_head	list;
+	struct device_node	*dev;
+	struct device_node	*interrupt_parent;
+};
+
+/**
+ * of_irq_init - Scan and init matching interrupt controllers in DT
+ * @matches: 0 terminated array of nodes to match and init function to call
+ *
+ * This function scans the device tree for matching interrupt controller nodes,
+ * and calls their initialization functions in order with parents first.
+ */
+void __init of_irq_init(const struct of_device_id *matches)
+{
+	struct device_node *np, *parent = NULL;
+	struct intc_desc *desc, *temp_desc;
+	struct list_head intc_desc_list, intc_parent_list;
+
+	INIT_LIST_HEAD(&intc_desc_list);
+	INIT_LIST_HEAD(&intc_parent_list);
+
+	for_each_matching_node(np, matches) {
+		if (!of_find_property(np, "interrupt-controller", NULL))
+			continue;
+		/*
+		 * Here, we allocate and populate an intc_desc with the node
+		 * pointer, interrupt-parent device_node etc.
+		 */
+		desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+		if (WARN_ON(!desc))
+			goto err;
+
+		desc->dev = np;
+		desc->interrupt_parent = of_irq_find_parent(np);
+		list_add_tail(&desc->list, &intc_desc_list);
+	}
+
+	/*
+	 * The root irq controller is the one without an interrupt-parent.
+	 * That one goes first, followed by the controllers that reference it,
+	 * followed by the ones that reference the 2nd level controllers, etc.
+	 */
+	while (!list_empty(&intc_desc_list)) {
+		/*
+		 * Process all controllers with the current 'parent'.
+		 * First pass will be looking for NULL as the parent.
+		 * The assumption is that NULL parent means a root controller.
+		 */
+		list_for_each_entry_safe(desc, temp_desc, &intc_desc_list, list) {
+			const struct of_device_id *match;
+			int ret;
+			of_irq_init_cb_t irq_init_cb;
+
+			if (desc->interrupt_parent != parent)
+				continue;
+
+			list_del(&desc->list);
+			match = of_match_node(matches, desc->dev);
+			if (WARN(!match->data,
+			    "of_irq_init: no init function for %s\n",
+			    match->compatible)) {
+				kfree(desc);
+				continue;
+			}
+
+			pr_debug("of_irq_init: init %s @ %p, parent %p\n",
+				 match->compatible,
+				 desc->dev, desc->interrupt_parent);
+			irq_init_cb = match->data;
+			ret = irq_init_cb(desc->dev, desc->interrupt_parent);
+			if (ret) {
+				kfree(desc);
+				continue;
+			}
+
+			/*
+			 * This one is now set up; add it to the parent list so
+			 * its children can get processed in a subsequent pass.
+			 */
+			list_add_tail(&desc->list, &intc_parent_list);
+		}
+
+		/* Get the next pending parent that might have children */
+		desc = list_first_entry(&intc_parent_list, typeof(*desc), list);
+		if (list_empty(&intc_parent_list) || !desc) {
+			pr_err("of_irq_init: children remain, but no parents\n");
+			break;
+		}
+		list_del(&desc->list);
+		parent = desc->dev;
+		kfree(desc);
+	}
+
+	list_for_each_entry_safe(desc, temp_desc, &intc_parent_list, list) {
+		list_del(&desc->list);
+		kfree(desc);
+	}
+err:
+	list_for_each_entry_safe(desc, temp_desc, &intc_desc_list, list) {
+		list_del(&desc->list);
+		kfree(desc);
+	}
+}

include/linux/of_irq.h

@@ -33,6 +33,8 @@ struct of_irq {
 	u32 specifier[OF_MAX_IRQ_SPEC]; /* Specifier copy */
 };
 
+typedef int (*of_irq_init_cb_t)(struct device_node *, struct device_node *);
+
 /*
  * Workarounds only applied to 32bit powermac machines
  */
@@ -73,6 +75,7 @@ extern int of_irq_to_resource_table(struct device_node *dev,
 		struct resource *res, int nr_irqs);
 extern struct device_node *of_irq_find_parent(struct device_node *child);
 
+extern void of_irq_init(const struct of_device_id *matches);
 
 #endif /* CONFIG_OF_IRQ */
 #endif /* CONFIG_OF */