net: dsa: felix: support half-duplex link modes

Ping tested:

  [   11.808455] mscc_felix 0000:00:00.5 swp0: Link is Up - 1Gbps/Full - flow control rx/tx
  [   11.816497] IPv6: ADDRCONF(NETDEV_CHANGE): swp0: link becomes ready

  [root@LS1028ARDB ~] # ethtool -s swp0 advertise 0x4
  [   18.844591] mscc_felix 0000:00:00.5 swp0: Link is Down
  [   22.048337] mscc_felix 0000:00:00.5 swp0: Link is Up - 100Mbps/Half - flow control off

  [root@LS1028ARDB ~] # ip addr add 192.168.1.1/24 dev swp0

  [root@LS1028ARDB ~] # ping 192.168.1.2
  PING 192.168.1.2 (192.168.1.2): 56 data bytes
  (...)
  ^C--- 192.168.1.2 ping statistics ---
  3 packets transmitted, 3 packets received, 0% packet loss
  round-trip min/avg/max = 0.383/0.611/1.051 ms

  [root@LS1028ARDB ~] # ethtool -s swp0 advertise 0x10
  [  355.637747] mscc_felix 0000:00:00.5 swp0: Link is Down
  [  358.788034] mscc_felix 0000:00:00.5 swp0: Link is Up - 1Gbps/Half - flow control off

  [root@LS1028ARDB ~] # ping 192.168.1.2
  PING 192.168.1.2 (192.168.1.2): 56 data bytes
  (...)
  ^C
  --- 192.168.1.2 ping statistics ---
  16 packets transmitted, 16 packets received, 0% packet loss
  round-trip min/avg/max = 0.301/0.384/1.138 ms
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/ocelot/felix.c

@@ -194,13 +194,15 @@ static void felix_phylink_validate(struct dsa_switch *ds, int port,
 		return;
 	}
 
-	/* No half-duplex. */
 	phylink_set_port_modes(mask);
 	phylink_set(mask, Autoneg);
 	phylink_set(mask, Pause);
 	phylink_set(mask, Asym_Pause);
+	phylink_set(mask, 10baseT_Half);
 	phylink_set(mask, 10baseT_Full);
+	phylink_set(mask, 100baseT_Half);
 	phylink_set(mask, 100baseT_Full);
+	phylink_set(mask, 1000baseT_Half);
 	phylink_set(mask, 1000baseT_Full);
 
 	if (state->interface == PHY_INTERFACE_MODE_INTERNAL ||

drivers/net/dsa/ocelot/felix_vsc9959.c

@@ -817,12 +817,9 @@ static void vsc9959_pcs_init_sgmii(struct phy_device *pcs,
 
 		phy_set_bits(pcs, MII_BMCR, BMCR_ANENABLE);
 	} else {
+		u16 if_mode = ENETC_PCS_IF_MODE_SGMII_EN;
 		int speed;
 
-		if (state->duplex == DUPLEX_HALF) {
-			phydev_err(pcs, "Half duplex not supported\n");
-			return;
-		}
 		switch (state->speed) {
 		case SPEED_1000:
 			speed = ENETC_PCS_SPEED_1000;
@@ -841,9 +838,9 @@ static void vsc9959_pcs_init_sgmii(struct phy_device *pcs,
 			return;
 		}
 
-		phy_write(pcs, ENETC_PCS_IF_MODE,
-			  ENETC_PCS_IF_MODE_SGMII_EN |
-			  ENETC_PCS_IF_MODE_SGMII_SPEED(speed));
+		if_mode |= ENETC_PCS_IF_MODE_SGMII_SPEED(speed);
+		if (state->duplex == DUPLEX_HALF)
+			if_mode |= ENETC_PCS_IF_MODE_DUPLEX_HALF;
 
 		phy_clear_bits(pcs, MII_BMCR, BMCR_ANENABLE);
 	}
@@ -870,15 +867,18 @@ static void vsc9959_pcs_init_2500basex(struct phy_device *pcs,
 				       unsigned int link_an_mode,
 				       const struct phylink_link_state *state)
 {
+	u16 if_mode = ENETC_PCS_IF_MODE_SGMII_SPEED(ENETC_PCS_SPEED_2500) |
+		      ENETC_PCS_IF_MODE_SGMII_EN;
+
 	if (link_an_mode == MLO_AN_INBAND) {
 		phydev_err(pcs, "AN not supported on 3.125GHz SerDes lane\n");
 		return;
 	}
 
-	phy_write(pcs, ENETC_PCS_IF_MODE,
-		  ENETC_PCS_IF_MODE_SGMII_EN |
-		  ENETC_PCS_IF_MODE_SGMII_SPEED(ENETC_PCS_SPEED_2500));
+	if (state->duplex == DUPLEX_HALF)
+		if_mode |= ENETC_PCS_IF_MODE_DUPLEX_HALF;
 
+	phy_write(pcs, ENETC_PCS_IF_MODE, if_mode);
 	phy_clear_bits(pcs, MII_BMCR, BMCR_ANENABLE);
 }
 
@@ -919,8 +919,11 @@ static void vsc9959_pcs_init(struct ocelot *ocelot, int port,
 	linkmode_set_bit_array(phy_basic_ports_array,
 			       ARRAY_SIZE(phy_basic_ports_array),
 			       pcs->supported);
+	linkmode_set_bit(ETHTOOL_LINK_MODE_10baseT_Half_BIT, pcs->supported);
 	linkmode_set_bit(ETHTOOL_LINK_MODE_10baseT_Full_BIT, pcs->supported);
+	linkmode_set_bit(ETHTOOL_LINK_MODE_100baseT_Half_BIT, pcs->supported);
 	linkmode_set_bit(ETHTOOL_LINK_MODE_100baseT_Full_BIT, pcs->supported);
+	linkmode_set_bit(ETHTOOL_LINK_MODE_1000baseT_Half_BIT, pcs->supported);
 	linkmode_set_bit(ETHTOOL_LINK_MODE_1000baseT_Full_BIT, pcs->supported);
 	if (pcs->interface == PHY_INTERFACE_MODE_2500BASEX ||
 	    pcs->interface == PHY_INTERFACE_MODE_USXGMII)

include/linux/fsl/enetc_mdio.h

@@ -15,6 +15,7 @@
 #define ENETC_PCS_IF_MODE_SGMII_EN		BIT(0)
 #define ENETC_PCS_IF_MODE_USE_SGMII_AN		BIT(1)
 #define ENETC_PCS_IF_MODE_SGMII_SPEED(x)	(((x) << 2) & GENMASK(3, 2))
+#define ENETC_PCS_IF_MODE_DUPLEX_HALF		BIT(3)
 
 /* Not a mistake, the SerDes PLL needs to be set at 3.125 GHz by Reset
  * Configuration Word (RCW, outside Linux control) for 2.5G SGMII mode. The PCS