netdev - Re: [PATCH net v1 1] net: macb: Avoid 20s boot delay by skipping MDIO bus registration for fixed-link PHY

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Message-ID: <379d10d5-468c-4d88-984e-df9ddc52f28e@lunn.ch>
Date: Sat, 12 Oct 2024 20:14:43 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...rochip.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	stable@...r.kernel.org, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
Subject: Re: [PATCH net v1 1] net: macb: Avoid 20s boot delay by skipping
 MDIO bus registration for fixed-link PHY

> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index f06babec04a0b..e4ee55bc53ba7 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -930,9 +930,6 @@ static int macb_mdiobus_register(struct macb *bp)
>  		return ret;
>  	}
> 
> -	if (of_phy_is_fixed_link(np))
> -		return mdiobus_register(bp->mii_bus);
> -
>  	/* Only create the PHY from the device tree if at least one PHY is
>  	 * described. Otherwise scan the entire MDIO bus. We do this to support
>  	 * old device tree that did not follow the best practices and did not
> @@ -953,8 +950,19 @@ static int macb_mdiobus_register(struct macb *bp)
> 
>  static int macb_mii_init(struct macb *bp)
>  {
> +	struct device_node *child, *np = bp->pdev->dev.of_node;
>  	int err = -ENXIO;
> 
> +	/* With fixed-link, we don't need to register the MDIO bus,
> +	 * except if we have a child named "mdio" in the device tree.
> +	 * In that case, some PHYs may be attached to the MACB's MDIO bus.

nitpick. It could be a switch on the MDIO bus, so "some devices may
be"

> +	 */
> +	child = of_get_child_by_name(np, "mdio");
> +	if (child)
> +		of_node_put(child);

The code now gets this node twice. You could add an optimisation patch
which passed child to macb_mdiobus_register().

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew