net: phy: at803x: Support downstream SFP cage

Add support for downstream SFP cages for AR8031 and AR8033. This is
primarily intended for fiber modules or direct-attach cables, however
copper modules which work in 1000Base-X mode may also function. Such
modules are allowed with a warning.
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/at803x.c

@@ -19,6 +19,8 @@
 #include <linux/regulator/of_regulator.h>
 #include <linux/regulator/driver.h>
 #include <linux/regulator/consumer.h>
+#include <linux/phylink.h>
+#include <linux/sfp.h>
 #include <dt-bindings/net/qca-ar803x.h>
 
 #define AT803X_SPECIFIC_FUNCTION_CONTROL	0x10
@@ -664,6 +666,55 @@ static int at8031_register_regulators(struct phy_device *phydev)
 	return 0;
 }
 
+static int at803x_sfp_insert(void *upstream, const struct sfp_eeprom_id *id)
+{
+	struct phy_device *phydev = upstream;
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(phy_support);
+	__ETHTOOL_DECLARE_LINK_MODE_MASK(sfp_support);
+	phy_interface_t iface;
+
+	linkmode_zero(phy_support);
+	phylink_set(phy_support, 1000baseX_Full);
+	phylink_set(phy_support, 1000baseT_Full);
+	phylink_set(phy_support, Autoneg);
+	phylink_set(phy_support, Pause);
+	phylink_set(phy_support, Asym_Pause);
+
+	linkmode_zero(sfp_support);
+	sfp_parse_support(phydev->sfp_bus, id, sfp_support);
+	/* Some modules support 10G modes as well as others we support.
+	 * Mask out non-supported modes so the correct interface is picked.
+	 */
+	linkmode_and(sfp_support, phy_support, sfp_support);
+
+	if (linkmode_empty(sfp_support)) {
+		dev_err(&phydev->mdio.dev, "incompatible SFP module inserted\n");
+		return -EINVAL;
+	}
+
+	iface = sfp_select_interface(phydev->sfp_bus, sfp_support);
+
+	/* Only 1000Base-X is supported by AR8031/8033 as the downstream SerDes
+	 * interface for use with SFP modules.
+	 * However, some copper modules detected as having a preferred SGMII
+	 * interface do default to and function in 1000Base-X mode, so just
+	 * print a warning and allow such modules, as they may have some chance
+	 * of working.
+	 */
+	if (iface == PHY_INTERFACE_MODE_SGMII)
+		dev_warn(&phydev->mdio.dev, "module may not function if 1000Base-X not supported\n");
+	else if (iface != PHY_INTERFACE_MODE_1000BASEX)
+		return -EINVAL;
+
+	return 0;
+}
+
+static const struct sfp_upstream_ops at803x_sfp_ops = {
+	.attach = phy_sfp_attach,
+	.detach = phy_sfp_detach,
+	.module_insert = at803x_sfp_insert,
+};
+
 static int at803x_parse_dt(struct phy_device *phydev)
 {
 	struct device_node *node = phydev->mdio.dev.of_node;
@@ -771,6 +822,11 @@ static int at803x_parse_dt(struct phy_device *phydev)
 			phydev_err(phydev, "failed to get VDDIO regulator\n");
 			return PTR_ERR(priv->vddio);
 		}
+
+		/* Only AR8031/8033 support 1000Base-X for SFP modules */
+		ret = phy_sfp_probe(phydev, &at803x_sfp_ops);
+		if (ret < 0)
+			return ret;
 	}
 
 	return 0;