From: Daniel Golle <daniel@makrotopia.org>
Date: Thu, 30 Jan 2025 05:38:31 +0000
Subject: [PATCH] net: phy: realtek: disable MDIO broadcast

RealTek's PHYs by default also listen on MDIO address 0 which is defined
as broadcast address. This can lead to problems if there is an actual PHY
(such as MT7981 built-in PHY) present at this address, as accessing that
PHY may then confuse the RealTek PHY.

Disabled listening on the MDIO broadcast address to avoid such problems.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
--- a/drivers/net/phy/realtek/realtek_main.c
+++ b/drivers/net/phy/realtek/realtek_main.c
@@ -849,6 +849,11 @@ static int rtl822xb_config_init(struct p
 			     phydev->host_interfaces) ||
 		    phydev->interface == PHY_INTERFACE_MODE_SGMII;
 
+	/* disable listening on MDIO broadcast address (0) */
+	ret = phy_clear_bits_mmd(phydev, MDIO_MMD_VEND2, 0xa430, BIT(13));
+	if (ret < 0)
+		return ret;
+
 	/* fill in possible interfaces */
 	__assign_bit(PHY_INTERFACE_MODE_2500BASEX, phydev->possible_interfaces,
 		     has_2500);
