diff --git a/drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c b/drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c
index 9b00bdc8ef1a..e368b2a36bac 100644
--- a/drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c
+++ b/drivers/gpu/drm/xe/xe_ttm_stolen_mgr.c
@@ -81,7 +81,7 @@ static u32 get_wopcm_size(struct xe_device *xe)
 	return wopcm_size;
 }
 
-static s64 detect_bar2_dgfx(struct xe_device *xe, struct xe_ttm_stolen_mgr *mgr)
+static u64 detect_bar2_dgfx(struct xe_device *xe, struct xe_ttm_stolen_mgr *mgr)
 {
 	struct xe_vram_region *tile_vram = xe_device_get_root_tile(xe)->mem.vram;
 	resource_size_t tile_io_start = xe_vram_region_io_start(tile_vram);
@@ -105,6 +105,8 @@ static s64 detect_bar2_dgfx(struct xe_device *xe, struct xe_ttm_stolen_mgr *mgr)
 		return 0;
 
 	stolen_size = tile_size - mgr->stolen_base;
+
+	xe_assert(xe, stolen_size > wopcm_size);
 	stolen_size -= wopcm_size;
 
 	/* Verify usage fits in the actual resource available */