Fixes XAUI/RXAUI lane alignment errors.
Issue causes dropped packets when trying to communicate over
fiber via SERDES lanes of port 9 and 10.
Errata document applies only to 88E6190X and 88E6390X devices.
Requires poking in undocumented registers.

Signed-off-by: Ante Knezic <redacted>
---
V4 : Rework as suggested by Vladimir Oltean [off-list ref]
     and Russell King [off-list ref]
 * print error in case of failure to apply erratum
 * use mdiobus_c45_write instead of mdiodev_c45_write
 * use bool variable instead of embedding a chip pointer inside
   pcs struct.
V3 : Rework to fit the new phylink_pcs infrastructure
V2 : Rework as suggested by Andrew Lunn [off-list ref] 
 * make int lanes[] const 
 * reorder prod_nums
 * update commit message to indicate we are dealing with
   undocumented Marvell registers and magic values
---
 drivers/net/dsa/mv88e6xxx/pcs-639x.c | 45 ++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/drivers/net/dsa/mv88e6xxx/pcs-639x.c b/drivers/net/dsa/mv88e6xxx/pcs-639x.c
index 98dd49dac421..ba373656bfe1 100644
--- a/drivers/net/dsa/mv88e6xxx/pcs-639x.c
+++ b/drivers/net/dsa/mv88e6xxx/pcs-639x.c

@@ -20,6 +20,7 @@ struct mv88e639x_pcs {
 	struct mdio_device mdio;
 	struct phylink_pcs sgmii_pcs;
 	struct phylink_pcs xg_pcs;
+	bool erratum_3_14;
 	bool supports_5g;
 	phy_interface_t interface;
 	unsigned int irq;

@@ -205,13 +206,53 @@ static void mv88e639x_sgmii_pcs_pre_config(struct phylink_pcs *pcs,
 	mv88e639x_sgmii_pcs_control_pwr(mpcs, false);
 }
 
+static int mv88e6390_erratum_3_14(struct mv88e639x_pcs *mpcs)
+{
+	const int lanes[] = { MV88E6390_PORT9_LANE0, MV88E6390_PORT9_LANE1,
+		MV88E6390_PORT9_LANE2, MV88E6390_PORT9_LANE3,
+		MV88E6390_PORT10_LANE0, MV88E6390_PORT10_LANE1,
+		MV88E6390_PORT10_LANE2, MV88E6390_PORT10_LANE3 };
+	int err, i;
+
+	/* 88e6190x and 88e6390x errata 3.14:
+	 * After chip reset, SERDES reconfiguration or SERDES core
+	 * Software Reset, the SERDES lanes may not be properly aligned
+	 * resulting in CRC errors
+	 */
+
+	for (i = 0; i < ARRAY_SIZE(lanes); i++) {
+		err = mdiobus_c45_write(mpcs->mdio.bus, lanes[i],
+					MDIO_MMD_PHYXS,
+					0xf054, 0x400C);
+		if (err)
+			return err;
+
+		err = mdiobus_c45_write(mpcs->mdio.bus, lanes[i],
+					MDIO_MMD_PHYXS,
+					0xf054, 0x4000);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 static int mv88e639x_sgmii_pcs_post_config(struct phylink_pcs *pcs,
 					   phy_interface_t interface)
 {
 	struct mv88e639x_pcs *mpcs = sgmii_pcs_to_mv88e639x_pcs(pcs);
+	int err;
 
 	mv88e639x_sgmii_pcs_control_pwr(mpcs, true);
 
+	if (mpcs->erratum_3_14) {
+		err = mv88e6390_erratum_3_14(mpcs);
+		if (err)
+			dev_err(mpcs->mdio.dev.parent,
+				"failed to apply erratum 3.14: %pe\n",
+				ERR_PTR(err));
+	}
+
 	return 0;
 }
 

@@ -524,6 +565,10 @@ static int mv88e6390_pcs_init(struct mv88e6xxx_chip *chip, int port)
 	mpcs->xg_pcs.ops = &mv88e6390_xg_pcs_ops;
 	mpcs->xg_pcs.neg_mode = true;
 
+	if (chip->info->prod_num == MV88E6XXX_PORT_SWITCH_ID_PROD_6190X ||
+	    chip->info->prod_num == MV88E6XXX_PORT_SWITCH_ID_PROD_6390X)
+		mpcs->erratum_3_14 = true;
+
 	err = mv88e639x_pcs_setup_irq(mpcs, chip, port);
 	if (err)
 		goto err_free;

-- 
2.11.0