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Date:   Tue, 12 Dec 2023 13:59:25 +0300
From:   Serge Semin <fancer.lancer@gmail.com>
To:     Andrew Halaney <ahalaney@redhat.com>
Cc:     Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Jose Abreu <joabreu@synopsys.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Giuseppe Cavallaro <peppe.cavallaro@st.com>,
        Andrew Lunn <andrew@lunn.ch>, netdev@vger.kernel.org,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] net: stmmac: Handle disabled MDIO busses from
 devicetree
Message-ID: <ggbqvhdhgl6wmuewqtwtgud7ubx2ypmnb3p6p6w7cy37mnnyxn@2eqd63s2t5ii>
References: <20231211-b4-stmmac-handle-mdio-enodev-v1-1-73c20c44f8d6@redhat.com>
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In-Reply-To: <20231211-b4-stmmac-handle-mdio-enodev-v1-1-73c20c44f8d6@redhat.com>
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On Mon, Dec 11, 2023 at 03:31:17PM -0600, Andrew Halaney wrote:
> 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@redhat.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;
>  	}

This can be implemented a bit simpler, more maintainable and saving
one indentations level:

	err = of_mdiobus_register(new_bus, mdio_node);
	if (err == -ENODEV) {
		err = 0;
		dev_warn(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;
	}

-Serge(y)

> 
> ---
> base-commit: bbd220ce4e29ed55ab079007cff0b550895258eb
> change-id: 20231211-b4-stmmac-handle-mdio-enodev-82168de68c6a
> 
> Best regards,
> -- 
> Andrew Halaney <ahalaney@redhat.com>
>