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

[Andrew Halaney]

On Tue, Dec 12, 2023 at 01:59:25PM +0300, Serge Semin wrote:
> 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 at 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");

Thanks for all your reviews, I agree this is cleaner!

I'm going to opt to use dev_info() here as this isn't something that's
wrong, just worth noting.

> 		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 at redhat.com>
> > 
>