linux-kernel - [PATCH net] net: stmmac: Handle disabled MDIO busses from devicetree

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Message-Id: <20231211-b4-stmmac-handle-mdio-enodev-v1-1-73c20c44f8d6@redhat.com>
Date:   Mon, 11 Dec 2023 15:31:17 -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,
        Andrew Halaney <ahalaney@...hat.com>
Subject: [PATCH net] 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>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c | 8 +++++++-
 1 file changed, 7 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..a39be15d41a8 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c
@@ -591,7 +591,13 @@ 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) {
+		if (err == -ENODEV) {
+			/* The bus is disabled in the devicetree, that's ok */
+			mdiobus_free(new_bus);
+			return 0;
+		}
+
 		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>