[PATCH v3] net: usb: lan78xx: scan all MDIO addresses on LAN7801

[Martin Pålsson]

The LAN7801 is designed exclusively for external PHYs (unlike the
LAN7800/LAN7850 which have internal PHYs), but lan78xx_mdio_init()
restricts PHY scanning to MDIO addresses 0-7 by setting phy_mask to
~(0xFF). This prevents discovery of external PHYs wired to addresses
outside that range.

One such case is the DP83TC814 100BASE-T1 PHY, which is typically
configured at MDIO address 10 via PHYAD bootstrap pins and goes
undetected with the current mask.

Remove the restrictive phy_mask assignment for the LAN7801 so that the
default mask of 0 applies, allowing all 32 MDIO addresses to be
scanned during bus registration.

Fixes: 02dc1f3d613d ("lan78xx: add LAN7801 MAC only support")

Signed-off-by: Martin Pålsson <martin@xxxxxxxxxxxx>
---
Changes in v3:
- Removed restrictive phy_mask assignment and comment, relying on the
  default mask of 0 to scan all 32 MDIO addresses (Maxime Chevallier)
- Link to v2: https://lore.kernel.org/r/20260216-lan78xx-phy-mask-fix-v2-1-6e97e59edd47@xxxxxxxxxxxx

Changes in v2:
- Added Fixes: tag
- Link to v1: https://lore.kernel.org/r/20260214-lan78xx-phy-mask-fix-v1-1-3baa100861e4@xxxxxxxxxxxx
---
 drivers/net/usb/lan78xx.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 00397a807393..065588c9cfa6 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2094,8 +2094,6 @@ static int lan78xx_mdio_init(struct lan78xx_net *dev)
 		dev->mdiobus->phy_mask = ~(1 << 1);
 		break;
 	case ID_REV_CHIP_ID_7801_:
-		/* scan thru PHYAD[2..0] */
-		dev->mdiobus->phy_mask = ~(0xFF);
 		break;
 	}
 

---
base-commit: ee5492fd88cfc079c19fbeac78e9e53b7f6c04f3
change-id: 20260214-lan78xx-phy-mask-fix-a4260de15a4c

Best regards,
-- 
Martin Pålsson <martin@xxxxxxxxxxxx>