diff --git a/drivers/gpu/drm/ast/ast_drv.h b/drivers/gpu/drm/ast/ast_drv.h
index 796dbb212a4138180f7bda2e50fb765f22805c93..8492b68e873c174cda6e99e70cf976a90e5ddaff 100644
--- a/drivers/gpu/drm/ast/ast_drv.h
+++ b/drivers/gpu/drm/ast/ast_drv.h
@@ -177,7 +177,7 @@ uint8_t ast_get_index_reg_mask(struct ast_private *ast,
 
 static inline void ast_open_key(struct ast_private *ast)
 {
-	ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xA1, 0xFF, 0x04);
+	ast_set_index_reg(ast, AST_IO_CRTC_PORT, 0x80, 0xA8);
 }
 
 #define AST_VIDMEM_SIZE_8M    0x00800000