ofwbus: remove arm64 ifdefs

Rather than using the DEVICE_IDENTIFY method, let's have other
ofwbus-using platforms add ofwbus0 explicitly in nexus, like arm64. This
gives them the same flexibility, e.g. if riscv starts supporting ACPI,
and cleans up the #ifdefs.

We were doing this already on riscv, but adjust the 'order' parameters.

Reviewed by:	andrew, jhb
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D38492

sys/arm/arm/nexus.c

@@ -182,8 +182,11 @@ nexus_attach(device_t dev)
 	if (rman_init(&irq_rman) || rman_manage_region(&irq_rman, 0, ~0))
 		panic("nexus_attach irq_rman");
 
+	/* First, add ofwbus0. */
+	device_add_child(dev, "ofwbus", 0);
+
 	/*
-	 * First, deal with the children we know about already
+	 * Next, deal with the children we know about already.
 	 */
 	bus_generic_probe(dev);
 	bus_generic_attach(dev);

sys/dev/ofw/ofwbus.c

@@ -54,12 +54,10 @@ __FBSDID("$FreeBSD$");
  * The ofwbus (which is a pseudo-bus actually) iterates over the nodes that
  * hang from the Open Firmware root node and adds them as devices to this bus
  * (except some special nodes which are excluded) so that drivers can be
- * attached to them.
+ * attached to them. There should be only one ofwbus in the system, added
+ * directly as a child of nexus0.
  */
 
-#ifndef __aarch64__
-static device_identify_t ofwbus_identify;
-#endif
 static device_probe_t ofwbus_probe;
 static device_attach_t ofwbus_attach;
 static bus_alloc_resource_t ofwbus_alloc_resource;
@@ -67,9 +65,6 @@ static bus_release_resource_t ofwbus_release_resource;
 
 static device_method_t ofwbus_methods[] = {
 	/* Device interface */
-#ifndef __aarch64__
-	DEVMETHOD(device_identify,	ofwbus_identify),
-#endif
 	DEVMETHOD(device_probe,		ofwbus_probe),
 	DEVMETHOD(device_attach,	ofwbus_attach),
 
@@ -87,28 +82,12 @@ EARLY_DRIVER_MODULE(ofwbus, nexus, ofwbus_driver, 0, 0,
     BUS_PASS_BUS + BUS_PASS_ORDER_MIDDLE);
 MODULE_VERSION(ofwbus, 1);
 
-#ifndef __aarch64__
-static void
-ofwbus_identify(driver_t *driver, device_t parent)
-{
-
-	/* Check if Open Firmware has been instantiated */
-	if (OF_peer(0) == 0)
-		return;
-
-	if (device_find_child(parent, "ofwbus", -1) == NULL)
-		BUS_ADD_CHILD(parent, 0, "ofwbus", -1);
-}
-#endif
-
 static int
 ofwbus_probe(device_t dev)
 {
 
-#ifdef __aarch64__
 	if (OF_peer(0) == 0)
 		return (ENXIO);
-#endif
 
 	device_set_desc(dev, "Open Firmware Device Tree");
 	return (BUS_PROBE_NOWILDCARD);

sys/powerpc/powerpc/nexus.c

@@ -146,6 +146,10 @@ nexus_attach(device_t dev)
 	    rman_manage_region(&mem_rman, 0, BUS_SPACE_MAXADDR) != 0)
 		panic("%s: failed to set up rmans.", __func__);
 
+	/* Add ofwbus0. */
+	device_add_child(dev, "ofwbus", 0);
+
+	/* Now, probe children. */
 	bus_generic_probe(dev);
 	bus_generic_attach(dev);
 

sys/riscv/riscv/nexus.c

@@ -165,9 +165,13 @@ nexus_attach(device_t dev)
 	if (rman_init(&irq_rman) || rman_manage_region(&irq_rman, 0, ~0))
 		panic("nexus_attach irq_rman");
 
-	nexus_add_child(dev, 8, "timer", 0);
+	/*
-	nexus_add_child(dev, 9, "rcons", 0);
+	 * Add direct children of nexus. Devices will be probed and attached
-	nexus_add_child(dev, 10, "ofwbus", 0);
+	 * through ofwbus0.
+	 */
+	nexus_add_child(dev, 0, "timer", 0);
+	nexus_add_child(dev, 1, "rcons", 0);
+	nexus_add_child(dev, 2, "ofwbus", 0);
 
 	bus_generic_probe(dev);
 	bus_generic_attach(dev);