net: dsa: mv88e6xxx: Add fix for erratum 5.2 of 88E6393X family

Add fix for erratum 5.2 of the 88E6393X (Amethyst) family: for 10gbase-r
mode, some undocumented registers need to be written some special
values.

Fixes: de776d0d ("net: dsa: mv88e6xxx: add support for mv88e6393x family")
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/serdes.c

@@ -1375,6 +1375,50 @@ static int mv88e6393x_serdes_erratum_4_8(struct mv88e6xxx_chip *chip, int lane)
 				      MV88E6393X_ERRATA_4_8_REG, reg);
 }
 
+static int mv88e6393x_serdes_erratum_5_2(struct mv88e6xxx_chip *chip, int lane,
+					 u8 cmode)
+{
+	static const struct {
+		u16 dev, reg, val, mask;
+	} fixes[] = {
+		{ MDIO_MMD_VEND1, 0x8093, 0xcb5a, 0xffff },
+		{ MDIO_MMD_VEND1, 0x8171, 0x7088, 0xffff },
+		{ MDIO_MMD_VEND1, 0x80c9, 0x311a, 0xffff },
+		{ MDIO_MMD_VEND1, 0x80a2, 0x8000, 0xff7f },
+		{ MDIO_MMD_VEND1, 0x80a9, 0x0000, 0xfff0 },
+		{ MDIO_MMD_VEND1, 0x80a3, 0x0000, 0xf8ff },
+		{ MDIO_MMD_PHYXS, MV88E6393X_SERDES_POC,
+		  MV88E6393X_SERDES_POC_RESET, MV88E6393X_SERDES_POC_RESET },
+	};
+	int err, i;
+	u16 reg;
+
+	/* mv88e6393x family errata 5.2:
+	 * For optimal signal integrity the following sequence should be applied
+	 * to SERDES operating in 10G mode. These registers only apply to 10G
+	 * operation and have no effect on other speeds.
+	 */
+	if (cmode != MV88E6393X_PORT_STS_CMODE_10GBASER)
+		return 0;
+
+	for (i = 0; i < ARRAY_SIZE(fixes); ++i) {
+		err = mv88e6390_serdes_read(chip, lane, fixes[i].dev,
+					    fixes[i].reg, &reg);
+		if (err)
+			return err;
+
+		reg &= ~fixes[i].mask;
+		reg |= fixes[i].val;
+
+		err = mv88e6390_serdes_write(chip, lane, fixes[i].dev,
+					     fixes[i].reg, reg);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 int mv88e6393x_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 			    bool on)
 {
@@ -1389,6 +1433,10 @@ int mv88e6393x_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 		if (err)
 			return err;
 
+		err = mv88e6393x_serdes_erratum_5_2(chip, lane, cmode);
+		if (err)
+			return err;
+
 		err = mv88e6393x_serdes_power_lane(chip, lane, true);
 		if (err)
 			return err;