drivers: of/base: move of_init to driver_init

Commit 5590f3196b29 ("drivers/core/of: Add symlink to device-tree from
devices with an OF node") adds the symlink `of_node` for each device
pointing to it's device tree node while creating/initialising it.

However the devicetree sysfs is created and setup in of_init which is
executed at core_initcall level. For all the devices created before
of_init, the following error is thrown:
	"Error -2(-ENOENT) creating of_node link"

Like many other components in driver model, initialize the sysfs support
for OF/devicetree from driver_init so that it's ready before any devices
are created.

Fixes: 5590f3196b29 ("drivers/core/of: Add symlink to device-tree from
	devices with an OF node")
Suggested-by: Rob Herring <robh+dt@kernel.org>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Robert Schwebel <r.schwebel@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/init.c

@@ -8,6 +8,7 @@
 #include <linux/device.h>
 #include <linux/init.h>
 #include <linux/memory.h>
+#include <linux/of.h>
 
 #include "base.h"
 
@@ -34,4 +35,5 @@ void __init driver_init(void)
 	cpu_dev_init();
 	memory_dev_init();
 	container_dev_init();
+	of_core_init();
 }

drivers/of/base.c

@@ -189,7 +189,7 @@ int __of_attach_node_sysfs(struct device_node *np)
 	return 0;
 }
 
-static int __init of_init(void)
+void __init of_core_init(void)
 {
 	struct device_node *np;
 
@@ -198,7 +198,8 @@ static int __init of_init(void)
 	of_kset = kset_create_and_add("devicetree", NULL, firmware_kobj);
 	if (!of_kset) {
 		mutex_unlock(&of_mutex);
-		return -ENOMEM;
+		pr_err("devicetree: failed to register existing nodes\n");
+		return;
 	}
 	for_each_of_allnodes(np)
 		__of_attach_node_sysfs(np);
@@ -207,10 +208,7 @@ static int __init of_init(void)
 	/* Symlink in /proc as required by userspace ABI */
 	if (of_root)
 		proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
-
-	return 0;
 }
-core_initcall(of_init);
 
 static struct property *__of_find_property(const struct device_node *np,
 					   const char *name, int *lenp)

include/linux/of.h

@@ -121,6 +121,8 @@ extern struct device_node *of_stdout;
 extern raw_spinlock_t devtree_lock;
 
 #ifdef CONFIG_OF
+void of_core_init(void);
+
 static inline bool is_of_node(struct fwnode_handle *fwnode)
 {
 	return fwnode && fwnode->type == FWNODE_OF;
@@ -376,6 +378,10 @@ bool of_console_check(struct device_node *dn, char *name, int index);
 
 #else /* CONFIG_OF */
 
+static inline void of_core_init(void)
+{
+}
+
 static inline bool is_of_node(struct fwnode_handle *fwnode)
 {
 	return false;