net: dsa: mv88e6xxx: implement USXGMII mode for mv88e6393x

Enable USXGMII mode for mv88e6393x chips. Tested on Marvell 88E6191X.
Signed-off-by: Michal Smulski <michal.smulski@ooma.com>
Link: https://lore.kernel.org/r/20230605174442.12493-1-msmulski2@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -812,11 +812,10 @@ static void mv88e6393x_phylink_get_caps(struct mv88e6xxx_chip *chip, int port,
 			if (!is_6361) {
 				__set_bit(PHY_INTERFACE_MODE_5GBASER, supported);
 				__set_bit(PHY_INTERFACE_MODE_10GBASER, supported);
+				__set_bit(PHY_INTERFACE_MODE_USXGMII, supported);
 				config->mac_capabilities |= MAC_5000FD |
 					MAC_10000FD;
 			}
-			/* FIXME: USXGMII is not supported yet */
-			/* __set_bit(PHY_INTERFACE_MODE_USXGMII, supported); */
 		}
 	}
 

drivers/net/dsa/mv88e6xxx/port.c

@@ -566,6 +566,9 @@ static int mv88e6xxx_port_set_cmode(struct mv88e6xxx_chip *chip, int port,
 	case PHY_INTERFACE_MODE_10GBASER:
 		cmode = MV88E6393X_PORT_STS_CMODE_10GBASER;
 		break;
+	case PHY_INTERFACE_MODE_USXGMII:
+		cmode = MV88E6393X_PORT_STS_CMODE_USXGMII;
+		break;
 	default:
 		cmode = 0;
 	}

drivers/net/dsa/mv88e6xxx/serdes.c

@@ -683,7 +683,8 @@ int mv88e6393x_serdes_get_lane(struct mv88e6xxx_chip *chip, int port)
 	    cmode == MV88E6XXX_PORT_STS_CMODE_SGMII ||
 	    cmode == MV88E6XXX_PORT_STS_CMODE_2500BASEX ||
 	    cmode == MV88E6393X_PORT_STS_CMODE_5GBASER ||
-	    cmode == MV88E6393X_PORT_STS_CMODE_10GBASER)
+	    cmode == MV88E6393X_PORT_STS_CMODE_10GBASER ||
+	    cmode == MV88E6393X_PORT_STS_CMODE_USXGMII)
 		lane = port;
 
 	return lane;
@@ -984,7 +985,42 @@ static int mv88e6393x_serdes_pcs_get_state_10g(struct mv88e6xxx_chip *chip,
 			state->speed = SPEED_10000;
 		state->duplex = DUPLEX_FULL;
 	}
+	return 0;
+}
+
+/* USXGMII registers for Marvell switch 88e639x are undocumented and this function is based
+ * on some educated guesses. It appears that there are no status bits related to
+ * autonegotiation complete or flow control.
+ */
+static int mv88e639x_serdes_pcs_get_state_usxgmii(struct mv88e6xxx_chip *chip,
+						  int port, int lane,
+						  struct phylink_link_state *state)
+{
+	u16 status, lp_status;
+	int err;
 
+	err = mv88e6390_serdes_read(chip, lane, MDIO_MMD_PHYXS,
+				    MV88E6390_USXGMII_PHY_STATUS, &status);
+	if (err) {
+		dev_err(chip->dev, "can't read Serdes USXGMII PHY status: %d\n", err);
+		return err;
+	}
+	dev_dbg(chip->dev, "USXGMII PHY status: 0x%x\n", status);
+
+	state->link = !!(status & MDIO_USXGMII_LINK);
+	state->an_complete = state->link;
+
+	if (state->link) {
+		err = mv88e6390_serdes_read(chip, lane, MDIO_MMD_PHYXS,
+					    MV88E6390_USXGMII_LP_STATUS, &lp_status);
+		if (err) {
+			dev_err(chip->dev, "can't read Serdes USXGMII LP status: %d\n", err);
+			return err;
+		}
+		dev_dbg(chip->dev, "USXGMII LP status: 0x%x\n", lp_status);
+		/* lp_status appears to include the "link" bit as per USXGMII spec. */
+		phylink_decode_usxgmii_word(state, lp_status);
+	}
 	return 0;
 }
 
@@ -1020,6 +1056,9 @@ int mv88e6393x_serdes_pcs_get_state(struct mv88e6xxx_chip *chip, int port,
 	case PHY_INTERFACE_MODE_10GBASER:
 		return mv88e6393x_serdes_pcs_get_state_10g(chip, port, lane,
 							   state);
+	case PHY_INTERFACE_MODE_USXGMII:
+		return mv88e639x_serdes_pcs_get_state_usxgmii(chip, port, lane,
+							   state);
 
 	default:
 		return -EOPNOTSUPP;
@@ -1173,6 +1212,7 @@ int mv88e6393x_serdes_irq_enable(struct mv88e6xxx_chip *chip, int port,
 		return mv88e6390_serdes_irq_enable_sgmii(chip, lane, enable);
 	case MV88E6393X_PORT_STS_CMODE_5GBASER:
 	case MV88E6393X_PORT_STS_CMODE_10GBASER:
+	case MV88E6393X_PORT_STS_CMODE_USXGMII:
 		return mv88e6393x_serdes_irq_enable_10g(chip, lane, enable);
 	}
 
@@ -1213,6 +1253,7 @@ irqreturn_t mv88e6393x_serdes_irq_status(struct mv88e6xxx_chip *chip, int port,
 		break;
 	case MV88E6393X_PORT_STS_CMODE_5GBASER:
 	case MV88E6393X_PORT_STS_CMODE_10GBASER:
+	case MV88E6393X_PORT_STS_CMODE_USXGMII:
 		err = mv88e6393x_serdes_irq_status_10g(chip, lane, &status);
 		if (err)
 			return err;
@@ -1477,7 +1518,8 @@ static int mv88e6393x_serdes_erratum_5_2(struct mv88e6xxx_chip *chip, int lane,
 	 * 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)
+	if (cmode != MV88E6393X_PORT_STS_CMODE_10GBASER &&
+	    cmode != MV88E6393X_PORT_STS_CMODE_USXGMII)
 		return 0;
 
 	for (i = 0; i < ARRAY_SIZE(fixes); ++i) {
@@ -1582,6 +1624,7 @@ int mv88e6393x_serdes_power(struct mv88e6xxx_chip *chip, int port, int lane,
 		break;
 	case MV88E6393X_PORT_STS_CMODE_5GBASER:
 	case MV88E6393X_PORT_STS_CMODE_10GBASER:
+	case MV88E6393X_PORT_STS_CMODE_USXGMII:
 		err = mv88e6390_serdes_power_10g(chip, lane, on);
 		break;
 	default:

drivers/net/dsa/mv88e6xxx/serdes.h

@@ -48,6 +48,10 @@
 #define MV88E6393X_10G_INT_LINK_CHANGE	BIT(2)
 #define MV88E6393X_10G_INT_STATUS	0x9001
 
+/* USXGMII */
+#define MV88E6390_USXGMII_LP_STATUS       0xf0a2
+#define MV88E6390_USXGMII_PHY_STATUS      0xf0a6
+
 /* 1000BASE-X and SGMII */
 #define MV88E6390_SGMII_BMCR		(0x2000 + MII_BMCR)
 #define MV88E6390_SGMII_BMSR		(0x2000 + MII_BMSR)