[PATCH net-next] net: phy: realtek: disable broadcast address feature of rtl8211f

[Zhiyuan Wan <kmlinuxm@gmail.com>]

This feature is automatically enabled after a reset of this
transceiver. When this feature is enabled, the phy not only
responds to the configured PHY address by pin states on board,
but also responds to address 0, the optional broadcast address
of the MDIO bus.

But some MDIO device like mt7530 switch chip (integrated in mt7621
SoC), also use address 0 to configure a specific port, when use
mt7530 and rtl8211f together, it usually causes address conflict,
leads to the port of rtl8211f stops working.

This patch disables broadcast address feature of rtl8211f, and
returns -ENODEV if using broadcast address (0) as phy address.

Hardware design hint:
This PHY only support address 1-7, and DO NOT tie all PHYAD pins
ground when you connect more than one PHY on a MDIO bus.
If you do that, this PHY will automatically take the first address
appeared on the MDIO bus as it's address, causing address conflict.

Signed-off-by: Zhiyuan Wan <kmlinuxm@gmail.com>
---
 drivers/net/phy/realtek.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index f65d7f1f3..0ef636d7b 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -31,6 +31,7 @@
 #define RTL8211F_PHYCR1				0x18
 #define RTL8211F_PHYCR2				0x19
 #define RTL8211F_INSR				0x1d
+#define RTL8211F_PHYAD0_EN			BIT(13)
 
 #define RTL8211F_LEDCR				0x10
 #define RTL8211F_LEDCR_MODE			BIT(15)
@@ -139,6 +140,17 @@ static int rtl821x_probe(struct phy_device *phydev)
 		return dev_err_probe(dev, PTR_ERR(priv->clk),
 				     "failed to get phy clock\n");
 
+	dev_dbg(dev, "disabling MDIO address 0 for this phy");
+	ret = phy_modify_paged(phydev, 0xa43, RTL8211F_PHYCR1,
+				       RTL8211F_PHYAD0_EN, 0);
+	if (ret < 0) {
+		return dev_err_probe(dev, PTR_ERR(ret),
+				     "disabling MDIO address 0 failed\n");
+	}
+	/* Deny broadcast address as PHY address */
+	if (phydev->mdio.addr == 0)
+		return -ENODEV;
+
 	ret = phy_read_paged(phydev, 0xa43, RTL8211F_PHYCR1);
 	if (ret < 0)
 		return ret;
-- 
2.30.2