powerpc/pseries: move to use bus_get_dev_root()

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

Cc: Nicholas Piggin <[e-mail]>
Cc: Christophe Leroy <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: [e-mail]
Acked-by: Michael Ellerman <[e-mail]> (powerpc)
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

arch/powerpc/platforms/pseries/pseries_energy.c

···
 static int __init pseries_energy_init(void)
 {
 	int cpu, err;
-	struct device *cpu_dev;
+	struct device *cpu_dev, *dev_root;
 
 	if (!firmware_has_feature(FW_FEATURE_BEST_ENERGY))
 		return 0; /* H_BEST_ENERGY hcall not supported */
 
 	/* Create the sysfs files */
-	err = device_create_file(cpu_subsys.dev_root,
-				&attr_cpu_activate_hint_list);
-	if (!err)
-		err = device_create_file(cpu_subsys.dev_root,
-				&attr_cpu_deactivate_hint_list);
+	dev_root = bus_get_dev_root(&cpu_subsys);
+	if (dev_root) {
+		err = device_create_file(dev_root, &attr_cpu_activate_hint_list);
+		if (!err)
+			err = device_create_file(dev_root, &attr_cpu_deactivate_hint_list);
+		put_device(dev_root);
+		if (err)
+			return err;
+	}
 
-	if (err)
-		return err;
 	for_each_possible_cpu(cpu) {
 		cpu_dev = get_cpu_device(cpu);
 		err = device_create_file(cpu_dev,
···
 static void __exit pseries_energy_cleanup(void)
 {
 	int cpu;
-	struct device *cpu_dev;
+	struct device *cpu_dev, *dev_root;
 
 	if (!sysfs_entries)
 		return;
 
 	/* Remove the sysfs files */
-	device_remove_file(cpu_subsys.dev_root, &attr_cpu_activate_hint_list);
-	device_remove_file(cpu_subsys.dev_root, &attr_cpu_deactivate_hint_list);
+	dev_root = bus_get_dev_root(&cpu_subsys);
+	if (dev_root) {
+		device_remove_file(dev_root, &attr_cpu_activate_hint_list);
+		device_remove_file(dev_root, &attr_cpu_deactivate_hint_list);
+		put_device(dev_root);
+	}
 
 	for_each_possible_cpu(cpu) {
 		cpu_dev = get_cpu_device(cpu);

arch/powerpc/platforms/pseries/suspend.c

···
  **/
 static int pseries_suspend_sysfs_register(struct device *dev)
 {
+	struct device *dev_root;
 	int rc;
 
 	if ((rc = subsys_system_register(&suspend_subsys, NULL)))
···
 	dev->id = 0;
 	dev->bus = &suspend_subsys;
 
-	if ((rc = device_create_file(suspend_subsys.dev_root, &dev_attr_hibernate)))
-		goto subsys_unregister;
+	dev_root = bus_get_dev_root(&suspend_subsys);
+	if (dev_root) {
+		rc = device_create_file(dev_root, &dev_attr_hibernate);
+		put_device(dev_root);
+		if (rc)
+			goto subsys_unregister;
+	}
 
 	return 0;