drm: Add reservation_object to drm_gem_object

Many users of drm_gem_object embed a struct reservation_object into
their subclassed struct, so let's add one to struct drm_gem_object.
This will allow removing the reservation object from the subclasses
and removing the ->gem_prime_res_obj callback.

With the addition, add a drm_gem_reservation_object_wait() helper
function for drivers to use in wait ioctls.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190202154158.10443-2-robh@kernel.org
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

Documentation/gpu/todo.rst

@@ -215,12 +215,12 @@ Might be good to also have some igt testcases for this.
 
 Contact: Daniel Vetter, Noralf Tronnes
 
-Put a reservation_object into drm_gem_object
+Remove the ->gem_prime_res_obj callback
 --------------------------------------------
 
-This would remove the need for the ->gem_prime_res_obj callback. It would also
-allow us to implement generic helpers for waiting for a bo, allowing for quite a
-bit of refactoring in the various wait ioctl implementations.
+The ->gem_prime_res_obj callback can be removed from drivers by using the
+reservation_object in the drm_gem_object. It may also be possible to use the
+generic drm_gem_reservation_object_wait helper for waiting for a bo.
 
 Contact: Daniel Vetter
 

drivers/gpu/drm/drm_gem.c

@@ -171,6 +171,10 @@ void drm_gem_private_object_init(struct drm_device *dev,
 	kref_init(&obj->refcount);
 	obj->handle_count = 0;
 	obj->size = size;
+	reservation_object_init(&obj->_resv);
+	if (!obj->resv)
+		obj->resv = &obj->_resv;
+
 	drm_vma_node_reset(&obj->vma_node);
 }
 EXPORT_SYMBOL(drm_gem_private_object_init);
@@ -687,6 +691,44 @@ drm_gem_object_lookup(struct drm_file *filp, u32 handle)
 }
 EXPORT_SYMBOL(drm_gem_object_lookup);
 
+/**
+ * drm_gem_reservation_object_wait - Wait on GEM object's reservation's objects
+ * shared and/or exclusive fences.
+ * @filep: DRM file private date
+ * @handle: userspace handle
+ * @wait_all: if true, wait on all fences, else wait on just exclusive fence
+ * @timeout: timeout value in jiffies or zero to return immediately
+ *
+ * Returns:
+ *
+ * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
+ * greater than 0 on success.
+ */
+long drm_gem_reservation_object_wait(struct drm_file *filep, u32 handle,
+				    bool wait_all, unsigned long timeout)
+{
+	long ret;
+	struct drm_gem_object *obj;
+
+	obj = drm_gem_object_lookup(filep, handle);
+	if (!obj) {
+		DRM_DEBUG("Failed to look up GEM BO %d\n", handle);
+		return -EINVAL;
+	}
+
+	ret = reservation_object_wait_timeout_rcu(obj->resv, wait_all,
+						  true, timeout);
+	if (ret == 0)
+		ret = -ETIME;
+	else if (ret > 0)
+		ret = 0;
+
+	drm_gem_object_put_unlocked(obj);
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_gem_reservation_object_wait);
+
 /**
  * drm_gem_close_ioctl - implementation of the GEM_CLOSE ioctl
  * @dev: drm_device
@@ -851,6 +893,7 @@ drm_gem_object_release(struct drm_gem_object *obj)
 	if (obj->filp)
 		fput(obj->filp);
 
+	reservation_object_fini(&obj->_resv);
 	drm_gem_free_mmap_offset(obj);
 }
 EXPORT_SYMBOL(drm_gem_object_release);

drivers/gpu/drm/drm_prime.c

@@ -504,6 +504,7 @@ struct dma_buf *drm_gem_prime_export(struct drm_device *dev,
 		.size = obj->size,
 		.flags = flags,
 		.priv = obj,
+		.resv = obj->resv,
 	};
 
 	if (dev->driver->gem_prime_res_obj)

include/drm/drm_gem.h

@@ -35,6 +35,7 @@
  */
 
 #include <linux/kref.h>
+#include <linux/reservation.h>
 
 #include <drm/drm_vma_manager.h>
 
@@ -262,6 +263,24 @@ struct drm_gem_object {
 	 */
 	struct dma_buf_attachment *import_attach;
 
+	/**
+	 * @resv:
+	 *
+	 * Pointer to reservation object associated with the this GEM object.
+	 *
+	 * Normally (@resv == &@_resv) except for imported GEM objects.
+	 */
+	struct reservation_object *resv;
+
+	/**
+	 * @_resv:
+	 *
+	 * A reservation object for this GEM object.
+	 *
+	 * This is unused for imported GEM objects.
+	 */
+	struct reservation_object _resv;
+
 	/**
 	 * @funcs:
 	 *
@@ -363,6 +382,8 @@ void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
 		bool dirty, bool accessed);
 
 struct drm_gem_object *drm_gem_object_lookup(struct drm_file *filp, u32 handle);
+long drm_gem_reservation_object_wait(struct drm_file *filep, u32 handle,
+				    bool wait_all, unsigned long timeout);
 int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
 			    u32 handle, u64 *offset);
 int drm_gem_dumb_destroy(struct drm_file *file,