net: phy: nxp-c45-tja11xx: run cable test with the PHY in test mode

For TJA1120, the enable bit for cable test is not writable if the PHY is
not in test mode.

Signed-off-by: Radu Pirea (NXP OSS) <radu-nicolae.pirea@oss.nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20230731091619.77961-10-radu-nicolae.pirea@oss.nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/nxp-c45-tja11xx.c

@@ -145,6 +145,7 @@
 
 #define VEND1_PORT_FUNC_ENABLES		0x8048
 #define PTP_ENABLE			BIT(3)
+#define PHY_TEST_ENABLE			BIT(0)
 
 #define VEND1_PORT_PTP_CONTROL		0x9000
 #define PORT_PTP_CONTROL_BYPASS		BIT(11)
@@ -1258,6 +1259,8 @@ static int nxp_c45_cable_test_start(struct phy_device *phydev)
 {
 	const struct nxp_c45_regmap *regmap = nxp_c45_get_regmap(phydev);
 
+	phy_set_bits_mmd(phydev, MDIO_MMD_VEND1,
+			 VEND1_PORT_FUNC_ENABLES, PHY_TEST_ENABLE);
 	return phy_set_bits_mmd(phydev, MDIO_MMD_VEND1, regmap->cable_test,
 				CABLE_TEST_ENABLE | CABLE_TEST_START);
 }
@@ -1299,6 +1302,8 @@ static int nxp_c45_cable_test_get_status(struct phy_device *phydev,
 
 	phy_clear_bits_mmd(phydev, MDIO_MMD_VEND1, regmap->cable_test,
 			   CABLE_TEST_ENABLE);
+	phy_clear_bits_mmd(phydev, MDIO_MMD_VEND1,
+			   VEND1_PORT_FUNC_ENABLES, PHY_TEST_ENABLE);
 
 	return nxp_c45_start_op(phydev);
 }