[PATCH net-next v2] net: dsa: mv88e6xxx: Add erratum 3.14 for 88E6390X and 88E6190X

[Ante Knezic]

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 <ante.knezic@xxxxxxxxxxx>
---
V2 : Rework as suggested by Andrew Lunn <andrew@xxxxxx> 
 * 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/serdes.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/net/dsa/mv88e6xxx/serdes.c b/drivers/net/dsa/mv88e6xxx/serdes.c
index 80167d53212f..b36049595c6b 100644
--- a/drivers/net/dsa/mv88e6xxx/serdes.c
+++ b/drivers/net/dsa/mv88e6xxx/serdes.c
@@ -829,6 +829,37 @@ static int mv88e6390_serdes_enable_checker(struct mv88e6xxx_chip *chip, int lane
 				      MV88E6390_PG_CONTROL, reg);
 }
 
+static int mv88e6390x_serdes_erratum_3_14(struct mv88e6xxx_chip *chip)
+{
+	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 = mv88e6390_serdes_write(chip, lanes[i],
+					     MDIO_MMD_PHYXS,
+					     0xf054, 0x400C);
+		if (err)
+			return err;
+
+		err = mv88e6390_serdes_write(chip, lanes[i],
+					     MDIO_MMD_PHYXS,
+					     0xf054, 0x4000);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 int mv88e6390_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 			   bool up)
 {
@@ -853,6 +884,12 @@ int mv88e6390_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 	if (!err && up)
 		err = mv88e6390_serdes_enable_checker(chip, lane);
 
+	if (!err && up) {
+		if (chip->info->prod_num == MV88E6XXX_PORT_SWITCH_ID_PROD_6190X ||
+		    chip->info->prod_num == MV88E6XXX_PORT_SWITCH_ID_PROD_6390X)
+			err = mv88e6390x_serdes_erratum_3_14(chip);
+	}
+
 	return err;
 }
 
-- 
2.11.0