drm/ttm: make ttm_tt unbind function return void.

The return value just led to BUG_ON, I think if a driver wants
to BUG_ON here it can do it itself. (don't BUG_ON).

Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

···
  * Called by ttm_tt_unbind() on behalf of ttm_bo_move_ttm() and
  * ttm_tt_destroy().
  */
-static int amdgpu_ttm_backend_unbind(struct ttm_tt *ttm)
+static void amdgpu_ttm_backend_unbind(struct ttm_tt *ttm)
 {
 	struct amdgpu_device *adev = amdgpu_ttm_adev(ttm->bdev);
 	struct amdgpu_ttm_tt *gtt = (void *)ttm;
···
 		amdgpu_ttm_tt_unpin_userptr(ttm);
 
 	if (gtt->offset == AMDGPU_BO_INVALID_OFFSET)
-		return 0;
+		return;
 
 	/* unbind shouldn't be done for GDS/GWS/OA in ttm_bo_clean_mm */
 	r = amdgpu_gart_unbind(adev, gtt->offset, ttm->num_pages);
 	if (r)
 		DRM_ERROR("failed to unbind %lu pages at 0x%08llX\n",
 			  gtt->ttm.ttm.num_pages, gtt->offset);
-	return r;
 }
 
 static void amdgpu_ttm_backend_destroy(struct ttm_tt *ttm)

drivers/gpu/drm/nouveau/nouveau_sgdma.c

···
 	return 0;
 }
 
-static int
+static void
 nv04_sgdma_unbind(struct ttm_tt *ttm)
 {
 	struct nouveau_sgdma_be *nvbe = (struct nouveau_sgdma_be *)ttm;
 	nouveau_mem_fini(nvbe->mem);
-	return 0;
 }
 
 static struct ttm_backend_func nv04_sgdma_backend = {

drivers/gpu/drm/qxl/qxl_ttm.c

···
 	return -1;
 }
 
-static int qxl_ttm_backend_unbind(struct ttm_tt *ttm)
+static void qxl_ttm_backend_unbind(struct ttm_tt *ttm)
 {
 	/* Not implemented */
-	return -1;
 }
 
 static void qxl_ttm_backend_destroy(struct ttm_tt *ttm)

drivers/gpu/drm/radeon/radeon_ttm.c

···
 	return 0;
 }
 
-static int radeon_ttm_backend_unbind(struct ttm_tt *ttm)
+static void radeon_ttm_backend_unbind(struct ttm_tt *ttm)
 {
 	struct radeon_ttm_tt *gtt = (void *)ttm;
 
···
 
 	if (gtt->userptr)
 		radeon_ttm_tt_unpin_userptr(ttm);
-
-	return 0;
 }
 
 static void radeon_ttm_backend_destroy(struct ttm_tt *ttm)

drivers/gpu/drm/ttm/ttm_agp_backend.c

···
 	return ret;
 }
 
-static int ttm_agp_unbind(struct ttm_tt *ttm)
+static void ttm_agp_unbind(struct ttm_tt *ttm)
 {
 	struct ttm_agp_backend *agp_be = container_of(ttm, struct ttm_agp_backend, ttm);
 
 	if (agp_be->mem) {
-		if (agp_be->mem->is_bound)
-			return agp_unbind_memory(agp_be->mem);
+		if (agp_be->mem->is_bound) {
+			agp_unbind_memory(agp_be->mem);
+			return;
+		}
 		agp_free_memory(agp_be->mem);
 		agp_be->mem = NULL;
 	}
-	return 0;
 }
 
 static void ttm_agp_destroy(struct ttm_tt *ttm)

drivers/gpu/drm/ttm/ttm_tt.c

···
 
 void ttm_tt_unbind(struct ttm_tt *ttm)
 {
-	int ret;
-
 	if (ttm->state == tt_bound) {
-		ret = ttm->func->unbind(ttm);
-		BUG_ON(ret);
+		ttm->func->unbind(ttm);
 		ttm->state = tt_unbound;
 	}
 }

drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c

···
 	return 0;
 }
 
-static int vmw_ttm_unbind(struct ttm_tt *ttm)
+static void vmw_ttm_unbind(struct ttm_tt *ttm)
 {
 	struct vmw_ttm_tt *vmw_be =
 		container_of(ttm, struct vmw_ttm_tt, dma_ttm.ttm);
···
 
 	if (vmw_be->dev_priv->map_mode == vmw_dma_map_bind)
 		vmw_ttm_unmap_dma(vmw_be);
-
-	return 0;
 }
 
 

include/drm/ttm/ttm_tt.h

···
 	 * Unbind previously bound backend pages. This function should be
 	 * able to handle differences between aperture and system page sizes.
 	 */
-	int (*unbind) (struct ttm_tt *ttm);
+	void (*unbind) (struct ttm_tt *ttm);
 
 	/**
 	 * struct ttm_backend_func member destroy