drm/ttm: revert "drm/ttm: make TT creation purely optional v3"

This reverts commit 2ddef17678.

As it turned out VMWGFX needs a much wider audit to fix this.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200811092400.188124-1-christian.koenig@amd.com

drivers/gpu/drm/ttm/ttm_bo.c

@@ -287,11 +287,12 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 	 */
 
 	if (!(new_man->flags & TTM_MEMTYPE_FLAG_FIXED)) {
-		bool zero = !(old_man->flags & TTM_MEMTYPE_FLAG_FIXED);
-
-		ret = ttm_tt_create(bo, zero);
-		if (ret)
-			goto out_err;
+		if (bo->ttm == NULL) {
+			bool zero = !(old_man->flags & TTM_MEMTYPE_FLAG_FIXED);
+			ret = ttm_tt_create(bo, zero);
+			if (ret)
+				goto out_err;
+		}
 
 		ret = ttm_tt_set_placement_caching(bo->ttm, mem->placement);
 		if (ret)
@@ -652,8 +653,13 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
 	placement.num_busy_placement = 0;
 	bdev->driver->evict_flags(bo, &placement);
 
-	if (!placement.num_placement && !placement.num_busy_placement)
-		return ttm_bo_pipeline_gutting(bo);
+	if (!placement.num_placement && !placement.num_busy_placement) {
+		ret = ttm_bo_pipeline_gutting(bo);
+		if (ret)
+			return ret;
+
+		return ttm_tt_create(bo, false);
+	}
 
 	evict_mem = bo->mem;
 	evict_mem.mm_node = NULL;
@@ -1192,8 +1198,13 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 	/*
 	 * Remove the backing store if no placement is given.
 	 */
-	if (!placement->num_placement && !placement->num_busy_placement)
-		return ttm_bo_pipeline_gutting(bo);
+	if (!placement->num_placement && !placement->num_busy_placement) {
+		ret = ttm_bo_pipeline_gutting(bo);
+		if (ret)
+			return ret;
+
+		return ttm_tt_create(bo, false);
+	}
 
 	/*
 	 * Check whether we need to move buffer.
@@ -1210,6 +1221,14 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 		ttm_flag_masked(&bo->mem.placement, new_flags,
 				~TTM_PL_MASK_MEMTYPE);
 	}
+	/*
+	 * We might need to add a TTM.
+	 */
+	if (bo->mem.mem_type == TTM_PL_SYSTEM && bo->ttm == NULL) {
+		ret = ttm_tt_create(bo, true);
+		if (ret)
+			return ret;
+	}
 	return 0;
 }
 EXPORT_SYMBOL(ttm_bo_validate);