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 <airlied@gmail.com>

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Mark Zhang <markz@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/gpu/host1x/bus.h b/drivers/gpu/host1x/bus.h
index 4099e99212c8..88fb1c4aac68 100644
--- a/drivers/gpu/host1x/bus.h
+++ b/drivers/gpu/host1x/bus.h
@@ -18,10 +18,10 @@
 #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);