gpu: host1x: Provide a proper struct bus_type

Previously the struct bus_type exported by the host1x infrastructure was
only a very basic skeleton. Turn that implementation into a more full-
fledged bus to support proper probe ordering and power management.

Note that the bus infrastructure needs to be available before any of the
drivers can be registered. This is automatically ensured if all drivers
are built as loadable modules (via symbol dependencies). If all drivers
are built-in there are no such guarantees and the link order determines
the initcall ordering. Adjust drivers/gpu/Makefile to make sure that the
host1x bus infrastructure is initialized prior to any of its users (only
drm/tegra currently).

v2: Fix building host1x and tegra-drm as modules
Reported-by: Dave Airlie <[e-mail]>

Reviewed-by: Sean Paul <[e-mail]>
Reviewed-by: Mark Zhang <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

drivers/gpu/Makefile

···
-obj-y			+= drm/ vga/
+# drm/tegra depends on host1x, so if both drivers are built-in care must be
+# taken to initialize them in the correct order. Link order is the only way
+# to ensure this currently.
 obj-$(CONFIG_TEGRA_HOST1X)	+= host1x/
+obj-y			+= drm/ vga/
 obj-$(CONFIG_IMX_IPUV3_CORE)	+= ipu-v3/

drivers/gpu/drm/tegra/drm.c

···
 };
 
 static struct host1x_driver host1x_drm_driver = {
-	.name = "drm",
+	.driver = {
+		.name = "drm",
+	},
 	.probe = host1x_drm_probe,
 	.remove = host1x_drm_remove,
 	.subdevs = host1x_drm_subdevs,

drivers/gpu/host1x/bus.c

···
 /**
  * host1x_device_parse_dt() - scan device tree and add matching subdevices
  */
-static int host1x_device_parse_dt(struct host1x_device *device)
+static int host1x_device_parse_dt(struct host1x_device *device,
+				  struct host1x_driver *driver)
 {
 	struct device_node *np;
 	int err;
 
 	for_each_child_of_node(device->dev.parent->of_node, np) {
-		if (of_match_node(device->driver->subdevs, np) &&
+		if (of_match_node(driver->subdevs, np) &&
 		    of_device_is_available(np)) {
 			err = host1x_subdev_add(device, np);
 			if (err < 0)
···
 	mutex_unlock(&device->clients_lock);
 	mutex_unlock(&device->subdevs_lock);
 
-	/*
-	 * When all subdevices have been registered, the composite device is
-	 * ready to be probed.
-	 */
 	if (list_empty(&device->subdevs)) {
-		err = device->driver->probe(device);
+		err = device_add(&device->dev);
 		if (err < 0)
-			dev_err(&device->dev, "probe failed for %ps: %d\n",
-				device->driver, err);
+			dev_err(&device->dev, "failed to add: %d\n", err);
 		else
-			device->bound = true;
+			device->registered = true;
 	}
 }
 
···
 				       struct host1x_subdev *subdev)
 {
 	struct host1x_client *client = subdev->client;
-	int err;
 
 	/*
 	 * If all subdevices have been activated, we're about to remove the
 	 * first active subdevice, so unload the driver first.
 	 */
-	if (list_empty(&device->subdevs) && device->bound) {
-		err = device->driver->remove(device);
-		if (err < 0)
-			dev_err(&device->dev, "remove failed: %d\n", err);
-
-		device->bound = false;
+	if (list_empty(&device->subdevs)) {
+		if (device->registered) {
+			device->registered = false;
+			device_del(&device->dev);
+		}
 	}
 
 	/*
···
 	return -ENODEV;
 }
 
-static struct bus_type host1x_bus_type = {
-	.name = "host1x",
+static int host1x_device_match(struct device *dev, struct device_driver *drv)
+{
+	return strcmp(dev_name(dev), drv->name) == 0;
+}
+
+static int host1x_device_probe(struct device *dev)
+{
+	struct host1x_driver *driver = to_host1x_driver(dev->driver);
+	struct host1x_device *device = to_host1x_device(dev);
+
+	if (driver->probe)
+		return driver->probe(device);
+
+	return 0;
+}
+
+static int host1x_device_remove(struct device *dev)
+{
+	struct host1x_driver *driver = to_host1x_driver(dev->driver);
+	struct host1x_device *device = to_host1x_device(dev);
+
+	if (driver->remove)
+		return driver->remove(device);
+
+	return 0;
+}
+
+static void host1x_device_shutdown(struct device *dev)
+{
+	struct host1x_driver *driver = to_host1x_driver(dev->driver);
+	struct host1x_device *device = to_host1x_device(dev);
+
+	if (driver->shutdown)
+		driver->shutdown(device);
+}
+
+static const struct dev_pm_ops host1x_device_pm_ops = {
+	.suspend = pm_generic_suspend,
+	.resume = pm_generic_resume,
+	.freeze = pm_generic_freeze,
+	.thaw = pm_generic_thaw,
+	.poweroff = pm_generic_poweroff,
+	.restore = pm_generic_restore,
 };
 
-int host1x_bus_init(void)
-{
-	return bus_register(&host1x_bus_type);
-}
-
-void host1x_bus_exit(void)
-{
-	bus_unregister(&host1x_bus_type);
-}
+struct bus_type host1x_bus_type = {
+	.name = "host1x",
+	.match = host1x_device_match,
+	.probe = host1x_device_probe,
+	.remove = host1x_device_remove,
+	.shutdown = host1x_device_shutdown,
+	.pm = &host1x_device_pm_ops,
+};
 
 static void __host1x_device_del(struct host1x_device *device)
 {
···
 	if (!device)
 		return -ENOMEM;
 
+	device_initialize(&device->dev);
+
 	mutex_init(&device->subdevs_lock);
 	INIT_LIST_HEAD(&device->subdevs);
 	INIT_LIST_HEAD(&device->active);
···
 
 	device->dev.coherent_dma_mask = host1x->dev->coherent_dma_mask;
 	device->dev.dma_mask = &device->dev.coherent_dma_mask;
+	dev_set_name(&device->dev, "%s", driver->driver.name);
 	device->dev.release = host1x_device_release;
-	dev_set_name(&device->dev, "%s", driver->name);
 	device->dev.bus = &host1x_bus_type;
 	device->dev.parent = host1x->dev;
 
-	err = device_register(&device->dev);
-	if (err < 0)
-		return err;
-
-	err = host1x_device_parse_dt(device);
+	err = host1x_device_parse_dt(device, driver);
 	if (err < 0) {
-		device_unregister(&device->dev);
+		kfree(device);
 		return err;
 	}
 
···
 static void host1x_device_del(struct host1x *host1x,
 			      struct host1x_device *device)
 {
-	device_unregister(&device->dev);
+	if (device->registered) {
+		device->registered = false;
+		device_del(&device->dev);
+	}
+
+	put_device(&device->dev);
 }
 
 static void host1x_attach_driver(struct host1x *host1x,
···
 	return 0;
 }
 
-int host1x_driver_register(struct host1x_driver *driver)
+int host1x_driver_register_full(struct host1x_driver *driver,
+				struct module *owner)
 {
 	struct host1x *host1x;
 
···
 
 	mutex_unlock(&devices_lock);
 
-	return 0;
+	driver->driver.bus = &host1x_bus_type;
+	driver->driver.owner = owner;
+
+	return driver_register(&driver->driver);
 }
-EXPORT_SYMBOL(host1x_driver_register);
+EXPORT_SYMBOL(host1x_driver_register_full);
 
 void host1x_driver_unregister(struct host1x_driver *driver)
 {

drivers/gpu/host1x/bus.h

···
 #ifndef HOST1X_BUS_H
 #define HOST1X_BUS_H
 
+struct bus_type;
 struct host1x;
 
-int host1x_bus_init(void);
-void host1x_bus_exit(void);
+extern struct bus_type host1x_bus_type;
 
 int host1x_register(struct host1x *host1x);
 int host1x_unregister(struct host1x *host1x);

drivers/gpu/host1x/dev.c

···
 {
 	int err;
 
-	err = host1x_bus_init();
+	err = bus_register(&host1x_bus_type);
 	if (err < 0)
 		return err;
 
···
 unregister_host1x:
 	platform_driver_unregister(&tegra_host1x_driver);
 unregister_bus:
-	host1x_bus_exit();
+	bus_unregister(&host1x_bus_type);
 	return err;
 }
 module_init(tegra_host1x_init);
···
 {
 	platform_driver_unregister(&tegra_mipi_driver);
 	platform_driver_unregister(&tegra_host1x_driver);
-	host1x_bus_exit();
+	bus_unregister(&host1x_bus_type);
 }
 module_exit(tegra_host1x_exit);
 

include/linux/host1x.h

···
 struct host1x_device;
 
 struct host1x_driver {
+	struct device_driver driver;
+
 	const struct of_device_id *subdevs;
 	struct list_head list;
-	const char *name;
 
 	int (*probe)(struct host1x_device *device);
 	int (*remove)(struct host1x_device *device);
+	void (*shutdown)(struct host1x_device *device);
 };
 
-int host1x_driver_register(struct host1x_driver *driver);
+static inline struct host1x_driver *
+to_host1x_driver(struct device_driver *driver)
+{
+	return container_of(driver, struct host1x_driver, driver);
+}
+
+int host1x_driver_register_full(struct host1x_driver *driver,
+				struct module *owner);
 void host1x_driver_unregister(struct host1x_driver *driver);
+
+#define host1x_driver_register(driver) \
+	host1x_driver_register_full(driver, THIS_MODULE)
 
 struct host1x_device {
 	struct host1x_driver *driver;
···
 	struct mutex clients_lock;
 	struct list_head clients;
 
-	bool bound;
+	bool registered;
 };
 
 static inline struct host1x_device *to_host1x_device(struct device *dev)