[PATCH net-next v2 2/2] net: phy: Add support for master-slave role configuration via device tree

[Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>]

Introduce support for configuring the master/slave role of PHYs based on
the `master-slave` property in the device tree. While this functionality
is necessary for Single Pair Ethernet (SPE) PHYs (1000/100/10Base-T1)
where hardware strap pins may be unavailable or incorrectly set, it
works for any PHY type. The property supports `forced-master` and
`forced-slave` values, allowing for predefined link role assignment.

Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
---
 drivers/net/phy/phy-core.c   | 29 +++++++++++++++++++++++++++++
 drivers/net/phy/phy_device.c |  3 +++
 include/linux/phy.h          |  1 +
 3 files changed, 33 insertions(+)

diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
index 1f98b6a96c153..296c446037144 100644
--- a/drivers/net/phy/phy-core.c
+++ b/drivers/net/phy/phy-core.c
@@ -412,6 +412,35 @@ void of_set_phy_eee_broken(struct phy_device *phydev)
 	phydev->eee_broken_modes = broken;
 }
 
+/**
+ * of_set_phy_master_slave - Set the master/slave mode of the PHY
+ *
+ * @phydev: The phy_device struct
+ *
+ * Set master/slave configuration of the PHY based on the device tree.
+ */
+void of_set_phy_master_slave(struct phy_device *phydev)
+{
+	struct device_node *node = phydev->mdio.dev.of_node;
+	const char *master;
+
+	if (!IS_ENABLED(CONFIG_OF_MDIO))
+		return;
+
+	if (!node)
+		return;
+
+	if (of_property_read_string(node, "master-slave", &master))
+		return;
+
+	if (strcmp(master, "forced-master") == 0)
+		phydev->master_slave_set = MASTER_SLAVE_CFG_MASTER_FORCE;
+	else if (strcmp(master, "forced-slave") == 0)
+		phydev->master_slave_set = MASTER_SLAVE_CFG_SLAVE_FORCE;
+	else
+		phydev_warn(phydev, "Unknown master-slave mode %s\n", master);
+}
+
 /**
  * phy_resolve_aneg_pause - Determine pause autoneg results
  *
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 560e338b307a4..8304f2781d5ae 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -3608,6 +3608,9 @@ static int phy_probe(struct device *dev)
 	 */
 	of_set_phy_eee_broken(phydev);
 
+	/* Get master/slave strap overrides */
+	of_set_phy_master_slave(phydev);
+
 	/* The Pause Frame bits indicate that the PHY can support passing
 	 * pause frames. During autonegotiation, the PHYs will determine if
 	 * they should allow pause frames to pass.  The MAC driver should then
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 4a9a11749c554..81701bdac44c1 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -1260,6 +1260,7 @@ size_t phy_speeds(unsigned int *speeds, size_t size,
 		  unsigned long *mask);
 void of_set_phy_supported(struct phy_device *phydev);
 void of_set_phy_eee_broken(struct phy_device *phydev);
+void of_set_phy_master_slave(struct phy_device *phydev);
 int phy_speed_down_core(struct phy_device *phydev);
 
 /**
-- 
2.39.2