diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index d5c98f79d58d..08ed0d08d03b 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -474,7 +474,10 @@ static void ast_set_color_reg(struct ast_private *ast,
 static void ast_set_crtthd_reg(struct ast_private *ast)
 {
 	/* Set Threshold */
-	if (ast->chip == AST2300 || ast->chip == AST2400 ||
+	if (ast->chip == AST2600) {
+		ast_set_index_reg(ast, AST_IO_CRTC_PORT, 0xa7, 0xe0);
+		ast_set_index_reg(ast, AST_IO_CRTC_PORT, 0xa6, 0xa0);
+	} else if (ast->chip == AST2300 || ast->chip == AST2400 ||
 	    ast->chip == AST2500) {
 		ast_set_index_reg(ast, AST_IO_CRTC_PORT, 0xa7, 0x78);
 		ast_set_index_reg(ast, AST_IO_CRTC_PORT, 0xa6, 0x60);