diff --git a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4-rev21.dts b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4-rev21.dts
index 6104cac5..ce2fe96d 100644
--- a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4-rev21.dts
+++ b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4-rev21.dts
@@ -29,6 +29,10 @@
 	model = "NanoPi M4";
 };
 
+&gmac {
+	tx_delay = <0x20>;
+};
+
 &sdhci {
 	mmc-hs200-1_8v;
 	/delete-property/ mmc-hs400-1_8v;