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 <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linuxppc-dev@lists.ozlabs.org
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Link: https://lore.kernel.org/r/20230313182918.1312597-14-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/powerpc/platforms/pseries/pseries_energy.c

@@ -300,20 +300,22 @@ static struct device_attribute attr_percpu_deactivate_hint =
 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);
+	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(cpu_subsys.dev_root,
-				&attr_cpu_deactivate_hint_list);
-
+			err = device_create_file(dev_root, &attr_cpu_deactivate_hint_list);
+		put_device(dev_root);
 		if (err)
 			return err;
+	}
+
 	for_each_possible_cpu(cpu) {
 		cpu_dev = get_cpu_device(cpu);
 		err = device_create_file(cpu_dev,
@@ -337,14 +339,18 @@ static int __init pseries_energy_init(void)
 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

@@ -143,6 +143,7 @@ static const struct platform_suspend_ops pseries_suspend_ops = {
  **/
 static int pseries_suspend_sysfs_register(struct device *dev)
 {
+	struct device *dev_root;
 	int rc;
 
 	if ((rc = subsys_system_register(&suspend_subsys, NULL)))
@@ -151,8 +152,13 @@ static int pseries_suspend_sysfs_register(struct device *dev)
 	dev->id = 0;
 	dev->bus = &suspend_subsys;
 
-	if ((rc = device_create_file(suspend_subsys.dev_root, &dev_attr_hibernate)))
+	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;