drm/radeon: Maintain prime import/export refcount for BOs

Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NChristopher James Halse Rogers <christopher.halse.rogers@canonical.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon.h

@@ -499,6 +499,7 @@ struct radeon_bo {
 	u32				tiling_flags;
 	u32				pitch;
 	int				surface_reg;
+	unsigned			prime_shared_count;
 	/* list of all virtual address to which this bo
 	 * is associated to
 	 */

drivers/gpu/drm/radeon/radeon_prime.c

@@ -77,6 +77,7 @@ struct drm_gem_object *radeon_gem_prime_import_sg_table(struct drm_device *dev,
 	list_add_tail(&bo->list, &rdev->gem.objects);
 	mutex_unlock(&rdev->gem.mutex);
 
+	bo->prime_shared_count = 1;
 	return &bo->gem_base;
 }
 
@@ -91,6 +92,9 @@ int radeon_gem_prime_pin(struct drm_gem_object *obj)
 
 	/* pin buffer into GTT */
 	ret = radeon_bo_pin(bo, RADEON_GEM_DOMAIN_GTT, NULL);
+	if (likely(ret == 0))
+		bo->prime_shared_count++;
+
 	radeon_bo_unreserve(bo);
 	return ret;
 }
@@ -105,6 +109,8 @@ void radeon_gem_prime_unpin(struct drm_gem_object *obj)
 		return;
 
 	radeon_bo_unpin(bo);
+	if (bo->prime_shared_count)
+		bo->prime_shared_count--;
 	radeon_bo_unreserve(bo);
 }