net: phy: nxp-c45-tja11xx: add TJA112XB SGMII PCS restart errata

TJA1120B/TJA1121B can achieve a stable operation of SGMII after
a startup event by putting the SGMII PCS into power down mode and
restart afterwards.

It is necessary to put the SGMII PCS into power down mode and back up.

Cc: stable@vger.kernel.org
Fixes: f1fe5df ("net: phy: nxp-c45-tja11xx: add TJA1120 support")
Signed-off-by: Andrei Botila <andrei.botila@oss.nxp.com>
Link: https://patch.msgid.link/20250304160619.181046-3-andrei.botila@oss.nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -114,6 +114,9 @@
 #define MII_BASIC_CONFIG_RMII		0x5
 #define MII_BASIC_CONFIG_MII		0x4
 
+#define VEND1_SGMII_BASIC_CONTROL	0xB000
+#define SGMII_LPM			BIT(11)
+
 #define VEND1_SYMBOL_ERROR_CNT_XTD	0x8351
 #define EXTENDED_CNT_EN			BIT(15)
 #define VEND1_MONITOR_STATUS		0xAC80
@@ -1598,11 +1601,11 @@ static int nxp_c45_set_phy_mode(struct phy_device *phydev)
 	return 0;
 }
 
-/* Errata: ES_TJA1120 and ES_TJA1121 Rev. 1.0 — 28 November 2024 Section 3.1 */
+/* Errata: ES_TJA1120 and ES_TJA1121 Rev. 1.0 — 28 November 2024 Section 3.1 & 3.2 */
 static void nxp_c45_tja1120_errata(struct phy_device *phydev)
 {
+	bool macsec_ability, sgmii_ability;
 	int silicon_version, sample_type;
-	bool macsec_ability;
 	int phy_abilities;
 	int ret = 0;
 
@@ -1619,6 +1622,7 @@ static void nxp_c45_tja1120_errata(struct phy_device *phydev)
 	phy_abilities = phy_read_mmd(phydev, MDIO_MMD_VEND1,
 				     VEND1_PORT_ABILITIES);
 	macsec_ability = !!(phy_abilities & MACSEC_ABILITY);
+	sgmii_ability = !!(phy_abilities & SGMII_ABILITY);
 	if ((!macsec_ability && silicon_version == 2) ||
 	    (macsec_ability && silicon_version == 1)) {
 		/* TJA1120/TJA1121 PHY configuration errata workaround.
@@ -1639,6 +1643,18 @@ static void nxp_c45_tja1120_errata(struct phy_device *phydev)
 
 		phy_write_mmd(phydev, MDIO_MMD_VEND1, 0x01F8, 0x0);
 		phy_write_mmd(phydev, MDIO_MMD_VEND1, 0x01F9, 0x0);
+
+		if (sgmii_ability) {
+			/* TJA1120B/TJA1121B SGMII PCS restart errata workaround.
+			 * Put SGMII PCS into power down mode and back up.
+			 */
+			phy_set_bits_mmd(phydev, MDIO_MMD_VEND1,
+					 VEND1_SGMII_BASIC_CONTROL,
+					 SGMII_LPM);
+			phy_clear_bits_mmd(phydev, MDIO_MMD_VEND1,
+					   VEND1_SGMII_BASIC_CONTROL,
+					   SGMII_LPM);
+		}
 	}
 }