[PATCH net] net: stmmac: Skip PHY attach if custom PCS is in use

When a platform provides a custom PCS via the pcs_init callback
(e.g., for USXGMII with in-band autoneg), the MAC's phylink_pcs
is already configured. In this case, phylink validates against
the PCS's supported interfaces and manages link state through
the PCS, so no traditional PHY device is needed.

Without this, stmmac_init_phy() falls through to the
no-phy-node path and errors out with "no phy found" when
the DT has no phy-handle for such interfaces.

Skip the PHY attach when priv->hw->phylink_pcs is already set
and no phy-handle is specified in the device tree, allowing
platform PCS implementations to handle the link autonomously.

Fixes: f0ef433fc264 ("net: stmmac: introduce pcs_init/pcs_exit stmmac operations")
Signed-off-by: Zxyan Zhu <redacted>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 2a0d7eff88d3..54c5281e91ab 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -1346,6 +1346,10 @@ static int stmmac_init_phy(struct net_device *dev)
 		int addr = priv->plat->phy_addr;
 		struct phy_device *phydev;
 
+		/* If a custom PCS is in use, no PHY is needed */
+		if (priv->hw->phylink_pcs)
+			return 0;
+
 		if (addr < 0) {
 			netdev_err(priv->dev, "no phy found\n");
 			return -ENODEV;

-- 
2.34.1