netdev - Re: [PATCH] net: mdio: of: Do not treat fixed-link as PHY

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Message-ID: <20200330163028.GE23477@lunn.ch>
Date:   Mon, 30 Mar 2020 18:30:28 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, f.fainelli@...il.com,
        hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net
Subject: Re: [PATCH] net: mdio: of: Do not treat fixed-link as PHY

On Mon, Mar 30, 2020 at 07:01:36PM +0300, Codrin Ciubotariu wrote:
> Some ethernet controllers, such as cadence's macb, have an embedded MDIO.
> For this reason, the ethernet PHY nodes are not under an MDIO bus, but
> directly under the ethernet node. Since these drivers might use
> of_mdiobus_child_is_phy(), we should fix this function by returning false
> if a fixed-link is found.

So i assume the problem occurs here:

static int macb_mdiobus_register(struct macb *bp)
{
        struct device_node *child, *np = bp->pdev->dev.of_node;

        /* 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
         * describe their network PHYs.
         */
        for_each_available_child_of_node(np, child)
                if (of_mdiobus_child_is_phy(child)) {
                        /* The loop increments the child refcount,
                         * decrement it before returning.
                         */
                        of_node_put(child);

                        return of_mdiobus_register(bp->mii_bus, np);
                }

        return mdiobus_register(bp->mii_bus);
}

I think a better solution is

        for_each_available_child_of_node(np, child)
+		if (of_phy_is_fixed_link(child)
+		   continue;
                if (of_mdiobus_child_is_phy(child)) {
                        /* The loop increments the child refcount,
                         * decrement it before returning.
                         */
                        of_node_put(child);

                        return of_mdiobus_register(bp->mii_bus, np);
                }

        return mdiobus_register(bp->mii_bus);
}

This problem is only an issue for macb, so keep the fix local to macb.

	Andrew