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

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Date: Tue, 12 Dec 2023 13:59:25 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Andrew Halaney <ahalaney@...hat.com>
Cc: 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>, Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org, 
	linux-stm32@...md-mailman.stormreply.com, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: stmmac: Handle disabled MDIO busses from
 devicetree

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@...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;
>  	}

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@...hat.com>
>