netdev - Re: [PATCH net-next v3 3/7] net: macb: parse PHY nodes found under an MDIO node

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Message-ID: <426a15dd-62de-9ffb-baed-c527b9aa9b70@gmail.com>
Date:   Fri, 24 Jul 2020 10:40:52 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     nicolas.ferre@...rochip.com, claudiu.beznea@...rochip.com,
        davem@...emloft.net, kuba@...nel.org, andrew@...n.ch,
        robh+dt@...nel.org, alexandre.belloni@...tlin.com,
        ludovic.desroches@...rochip.com
Subject: Re: [PATCH net-next v3 3/7] net: macb: parse PHY nodes found under an
 MDIO node

On 7/24/20 3:50 AM, Codrin Ciubotariu wrote:
> The MACB embeds an MDIO bus controller. For this reason, the PHY nodes
> were represented as sub-nodes in the MACB node. Generally, the
> Ethernet controller is different than the MDIO controller, so the PHYs
> are probed by a separate MDIO driver. Since adding the PHY nodes directly
> under the ETH node became deprecated, we adjust the MACB driver to look
> for an MDIO node and register the subnode MDIO devices.
> 
> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
> ---
> 
> Changes in v3:
>  - moved the check for the mdio node at the beginnging of
>    macb_mdiobus_register(). This way, the mdio devices will be probed even
>    if macb is a fixed-link
> 
> Changes in v2:
>  - readded newline removed by mistake;
> 
>  drivers/net/ethernet/cadence/macb_main.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index 89fe7af5e408..cb0b3637651c 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -740,6 +740,16 @@ static int macb_mii_probe(struct net_device *dev)
>  static int macb_mdiobus_register(struct macb *bp)
>  {
>  	struct device_node *child, *np = bp->pdev->dev.of_node;
> +	struct device_node *mdio_node;
> +	int ret;
> +
> +	/* if an MDIO node is present, it should contain the PHY nodes */
> +	mdio_node = of_get_child_by_name(np, "mdio");
> +	if (mdio_node) {
> +		ret = of_mdiobus_register(bp->mii_bus, mdio_node);
> +		of_node_put(mdio_node);
> +		return ret;
> +	}

This does take care of registering the MDIO bus controller when present
as a sub-node, however if you also plan on making use of fixed-link, we
will have already returned.

>  
>  	if (of_phy_is_fixed_link(np))
>  		return mdiobus_register(bp->mii_bus);
> 

Really not sure what this is achieving, because we start off assuming
that we have an OF driven configuration, but later on we register the
MDIO bus with mdiobus_register() (and not of_mdiobus_register()), so no
scanning of the MDIO bus will happen.

How does the driver currently support being provided a fixed-link
property? Should not we at least have this pattern:

         */
        if (of_phy_is_fixed_link(dn)) {
                ret = of_phy_register_fixed_link(dn);
                if (ret)
			return ret;

                priv->phy_dn = dn;
        }

It does not look like you are breaking anything here, because it does
not look like this works at all.
-- 
Florian