of/selftest: Add a test for duplicate phandles

All phandles in the tree should be unique. Add a testcase to make sure
that this is so.

Note: this testcase fails on the current kernel because the selftest
code itself ends up adding duplicate phandles. Before this testcase is
merged the selftest code needs to be modified to resolve phandles before
adding them.
Signed-off-by: Grant Likely <grant.likely@linaro.org>
Cc: Pantelis Antoniou <pantelis.antoniou@konsulko.com>

drivers/of/selftest.c

@@ -7,6 +7,7 @@
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/errno.h>
+#include <linux/hashtable.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_fdt.h>
@@ -192,6 +193,51 @@ static void __init of_selftest_check_tree_linkage(void)
 	pr_debug("allnodes list size (%i); sibling lists size (%i)\n", allnode_count, child_count);
 }
 
+struct node_hash {
+	struct hlist_node node;
+	struct device_node *np;
+};
+
+static void __init of_selftest_check_phandles(void)
+{
+	struct device_node *np;
+	struct node_hash *nh;
+	struct hlist_node *tmp;
+	int i, dup_count = 0, phandle_count = 0;
+	DECLARE_HASHTABLE(ht, 8);
+
+	hash_init(ht);
+	for_each_of_allnodes(np) {
+		if (!np->phandle)
+			continue;
+
+		hash_for_each_possible(ht, nh, node, np->phandle) {
+			if (nh->np->phandle == np->phandle) {
+				pr_info("Duplicate phandle! %i used by %s and %s\n",
+					np->phandle, nh->np->full_name, np->full_name);
+				dup_count++;
+				break;
+			}
+		}
+
+		nh = kzalloc(sizeof(*nh), GFP_KERNEL);
+		if (WARN_ON(!nh))
+			return;
+
+		nh->np = np;
+		hash_add(ht, &nh->node, np->phandle);
+		phandle_count++;
+	}
+	selftest(dup_count == 0, "Found %i duplicates in %i phandles\n",
+		 dup_count, phandle_count);
+
+	/* Clean up */
+	hash_for_each_safe(ht, i, tmp, nh, node) {
+		hash_del(&nh->node);
+		kfree(nh);
+	}
+}
+
 static void __init of_selftest_parse_phandle_with_args(void)
 {
 	struct device_node *np;
@@ -825,6 +871,7 @@ static int __init of_selftest(void)
 
 	pr_info("start of selftest - you will see error messages\n");
 	of_selftest_check_tree_linkage();
+	of_selftest_check_phandles();
 	of_selftest_find_node_by_name();
 	of_selftest_dynamic();
 	of_selftest_parse_phandle_with_args();