net: dsa: sja1105: support switching between SGMII and 2500BASE-X

Vladimir Oltean suggests that sja1105 can support switching between
SGMII and 2500BASE-X modes. Augment sja1105_phylink_get_caps() to
fill in both interface modes if they can be supported.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/sja1105_main.c

@@ -1396,6 +1396,7 @@ static void sja1105_phylink_get_caps(struct dsa_switch *ds, int port,
 {
 	struct sja1105_private *priv = ds->priv;
 	struct sja1105_xmii_params_entry *mii;
+	phy_interface_t phy_mode;
 
 	/* This driver does not make use of the speed, duplex, pause or the
 	 * advertisement in its mac_config, so it is safe to mark this driver
@@ -1403,11 +1404,27 @@ static void sja1105_phylink_get_caps(struct dsa_switch *ds, int port,
 	 */
 	config->legacy_pre_march2020 = false;
 
-	/* The SJA1105 MAC programming model is through the static config
-	 * (the xMII Mode table cannot be dynamically reconfigured), and
-	 * we have to program that early.
-	 */
-	__set_bit(priv->phy_mode[port], config->supported_interfaces);
+	phy_mode = priv->phy_mode[port];
+	if (phy_mode == PHY_INTERFACE_MODE_SGMII ||
+	    phy_mode == PHY_INTERFACE_MODE_2500BASEX) {
+		/* Changing the PHY mode on SERDES ports is possible and makes
+		 * sense, because that is done through the XPCS. We allow
+		 * changes between SGMII and 2500base-X.
+		 */
+		if (priv->info->supports_sgmii[port])
+			__set_bit(PHY_INTERFACE_MODE_SGMII,
+				  config->supported_interfaces);
+
+		if (priv->info->supports_2500basex[port])
+			__set_bit(PHY_INTERFACE_MODE_2500BASEX,
+				  config->supported_interfaces);
+	} else {
+		/* The SJA1105 MAC programming model is through the static
+		 * config (the xMII Mode table cannot be dynamically
+		 * reconfigured), and we have to program that early.
+		 */
+		__set_bit(phy_mode, config->supported_interfaces);
+	}
 
 	/* The MAC does not support pause frames, and also doesn't
 	 * support half-duplex traffic modes.