netdev - [PATCH net v2] net: stmmac: Handle disabled MDIO busses from devicetree

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Date: Tue, 12 Dec 2023 16:18:33 -0600
From: Andrew Halaney <ahalaney@...hat.com>
To: Alexandre Torgue <alexandre.torgue@...s.st.com>, 
 Jose Abreu <joabreu@...opsys.com>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Maxime Coquelin <mcoquelin.stm32@...il.com>, 
 Giuseppe Cavallaro <peppe.cavallaro@...com>
Cc: Andrew Lunn <andrew@...n.ch>, Serge Semin <fancer.lancer@...il.com>, 
 netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Simon Horman <horms@...nel.org>, Andrew Halaney <ahalaney@...hat.com>
Subject: [PATCH net v2] net: stmmac: Handle disabled MDIO busses from
 devicetree

Many hardware configurations have the MDIO bus disabled, and are instead
using some other MDIO bus to talk to the MAC's phy.

of_mdiobus_register() returns -ENODEV in this case. Let's handle it
gracefully instead of failing to probe the MAC.

Fixes: 47dd7a540b8a ("net: add support for STMicroelectronics Ethernet controllers.")
Signed-off-by: Andrew Halaney <ahalaney@...hat.com>
---
Changes in v2:
- Improve error handling code (Serge)
- Fix malformed Fixes tag (Simon)
- Link to v1: https://lore.kernel.org/r/20231211-b4-stmmac-handle-mdio-enodev-v1-1-73c20c44f8d6@redhat.com
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
index fa9e7e7040b9..0542cfd1817e 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -591,7 +591,11 @@ int stmmac_mdio_register(struct net_device *ndev)
 	new_bus->parent = priv->device;

 	err = of_mdiobus_register(new_bus, mdio_node);
-	if (err != 0) {
+	if (err == -ENODEV) {
+		err = 0;
+		dev_info(dev, "MDIO bus is disabled\n");
+		goto bus_register_fail;
+	} else if (err) {
 		dev_err_probe(dev, err, "Cannot register the MDIO bus\n");
 		goto bus_register_fail;
 	}

---
base-commit: bbd220ce4e29ed55ab079007cff0b550895258eb
change-id: 20231211-b4-stmmac-handle-mdio-enodev-82168de68c6a

Best regards,
-- 
Andrew Halaney <ahalaney@...hat.com>