MII phy_ports are not meant to be connected directly to a link partner.
They are meant to feed into some media converter devices that will
expose an MDI phy_port, so far we only support SFP modules for that.

In the case an MDI phy_port is backed by an MII port (e.g. a SFP
module's port, backed by the SFP cage port), let's keep track of the
port id of the MII port backing it.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 drivers/net/phy/phy_device.c | 29 +++++++++++++++++++++++++++--
 drivers/net/phy/phylink.c    |  5 +++++
 include/linux/phy.h          |  4 ++++
 include/linux/phy_port.h     |  3 +++
 4 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index b17e924b8d67..3da6872ebbba 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1493,6 +1493,7 @@ static int phy_sfp_connect_phy(void *upstream, struct phy_device *phy)
 	int ret;
 
 	phydev->has_sfp_mod_phy = true;
+	phy_set_upstream_port(phy, phydev->sfp_cage_port);
 
 	/* If we aren't attached to a netdev, we can't add the SFP PHY to its
 	 * topology.
@@ -1526,6 +1527,8 @@ static void phy_sfp_disconnect_phy(void *upstream, struct phy_device *phy)
 
 	if (dev)
 		phy_link_topo_del_phy(dev, phy);
+
+	phy_set_upstream_port(phy, NULL);
 }
 
 /**
@@ -1661,6 +1664,8 @@ static int phy_add_sfp_mod_port(struct phy_device *phydev)
 	 */
 	phydev->mod_port = port;
 
+	port->upstream_port = phydev->sfp_cage_port;
+
 	return 0;
 }
 
@@ -1813,6 +1818,8 @@ static int phy_sfp_probe(struct phy_device *phydev)
 		}
 	}
 
+	phydev->sfp_cage_port = port;
+
 	ret = sfp_bus_add_upstream(bus, phydev, &sfp_phydev_ops);
 	if (ret)
 		goto out_port;
@@ -1822,14 +1829,13 @@ static int phy_sfp_probe(struct phy_device *phydev)
 	 */
 	sfp_bus_put(bus);
 
-	phydev->sfp_cage_port = port;
-
 	return ret;
 
 out_port:
 	if (port) {
 		phy_del_port(phydev, port);
 		phy_port_destroy(port);
+		phydev->sfp_cage_port = NULL;
 	}
 out_sfp:
 	sfp_bus_put(bus);
@@ -3721,6 +3727,25 @@ struct phy_port *phy_get_sfp_port(struct phy_device *phydev)
 }
 EXPORT_SYMBOL_GPL(phy_get_sfp_port);
 
+/**
+ * phy_set_upstream_port() - Sets the phy_port controlling the MII this PHY is
+ *			     attached to.
+ * @phydev: pointer to the PHY device we set the upstream of.
+ * @port: The phy_port upstream of this PHY, can be NULL.
+ */
+void phy_set_upstream_port(struct phy_device *phydev, struct phy_port *port)
+{
+	struct phy_port *local_port;
+
+	ASSERT_RTNL();
+
+	phydev->upstream_port = port;
+
+	phy_for_each_port(phydev, local_port)
+		local_port->upstream_port = port;
+}
+EXPORT_SYMBOL_GPL(phy_set_upstream_port);
+
 /**
  * fwnode_mdio_find_device - Given a fwnode, find the mdio_device
  * @fwnode: pointer to the mdio_device's fwnode
diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 08203683c6e5..a5f025187afa 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -3959,6 +3959,8 @@ static int phylink_add_sfp_mod_port(struct phylink *pl)
 		}
 	}
 
+	port->upstream_port = pl->sfp_cage_port;
+
 	pl->mod_port = port;
 
 	return 0;
@@ -4062,6 +4064,8 @@ static int phylink_sfp_connect_phy(void *upstream, struct phy_device *phy)
 	phy_interface_and(phy->host_interfaces, phylink_sfp_interfaces,
 			  pl->config->supported_interfaces);
 
+	phy_set_upstream_port(phy, pl->sfp_cage_port);
+
 	/* Do the initial configuration */
 	return phylink_sfp_config_phy(pl, phy);
 }
@@ -4070,6 +4074,7 @@ static void phylink_sfp_disconnect_phy(void *upstream,
 				       struct phy_device *phydev)
 {
 	phylink_disconnect_phy(upstream);
+	phy_set_upstream_port(phydev, NULL);
 }
 
 static const struct sfp_upstream_ops sfp_phylink_ops = {
diff --git a/include/linux/phy.h b/include/linux/phy.h
index dfe0326eab27..741ca7a0a257 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -597,6 +597,7 @@ struct phy_oatc14_sqi_capability {
  * @sfp_bus: SFP bus attached to this PHY's fiber port
  * @sfp_cage_port: The phy_port connected to the downstream SFP cage
  * @mod_port: phy_port representing the SFP module, if it is phy-less
+ * @upstream_port: phy_port this PHY's MII attaches to, if any
  * @attached_dev: The attached enet driver's device instance ptr
  * @adjust_link: Callback for the enet controller to respond to changes: in the
  *               link state.
@@ -791,6 +792,7 @@ struct phy_device {
 	struct sfp_bus *sfp_bus;
 	struct phy_port *sfp_cage_port;
 	struct phy_port *mod_port;
+	struct phy_port *upstream_port;
 	struct phylink *phylink;
 	struct net_device *attached_dev;
 	struct mii_timestamper *mii_ts;
@@ -2474,6 +2476,8 @@ int __phy_hwtstamp_set(struct phy_device *phydev,
 
 struct phy_port *phy_get_sfp_port(struct phy_device *phydev);
 
+void phy_set_upstream_port(struct phy_device *phydev, struct phy_port *port);
+
 /**
  * phy_module_driver() - Helper macro for registering PHY drivers
  * @__phy_drivers: array of PHY drivers to register
diff --git a/include/linux/phy_port.h b/include/linux/phy_port.h
index 4e2a3fdd2f2e..8f45c031cbc1 100644
--- a/include/linux/phy_port.h
+++ b/include/linux/phy_port.h
@@ -40,6 +40,8 @@ struct phy_port_ops {
  * @head: Used by the port's parent to list ports
  * @parent_type: The type of device this port is directly connected to
  * @phy: If the parent is PHY_PORT_PHYDEV, the PHY controlling that port
+ * @upstream_port: Indicates the MII port that feeds this port, if any,
+ *		   e.g. the SFP cage port for a SFP module port.
  * @ops: Callback ops implemented by the port controller
  * @pairs: The number of  pairs this port has, 0 if not applicable
  * @mediums: Bitmask of the physical mediums this port provides access to
@@ -59,6 +61,7 @@ struct phy_port {
 	union {
 		struct phy_device *phy;
 	};
+	struct phy_port *upstream_port;
 
 	const struct phy_port_ops *ops;
 
-- 
2.55.0