diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index b9acee214bb6..bb8631558181 100644
--- a/drivers/net/ethernet/socionext/netsec.c
+++ b/drivers/net/ethernet/socionext/netsec.c
@@ -1845,6 +1845,17 @@ static int netsec_of_probe(struct platform_device *pdev,
 		return err;
 	}
 
+	/*
+	 * SynQuacer is physically configured with TX and RX delays
+	 * but the standard firmware claimed otherwise for a long
+	 * time, ignore it.
+	 */
+	if (of_machine_is_compatible("socionext,developer-box") &&
+	    priv->phy_interface != PHY_INTERFACE_MODE_RGMII_ID) {
+		dev_warn(&pdev->dev, "Outdated firmware reports incorrect PHY mode, overriding\n");
+		priv->phy_interface = PHY_INTERFACE_MODE_RGMII_ID;
+	}
+
 	priv->phy_np = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
 	if (!priv->phy_np) {
 		dev_err(&pdev->dev, "missing required property 'phy-handle'\n");