[PATCH 2/2] net: phy: atheros: avoid error in ar803x_of_init() when PHY has no OF node

[Ramon Fried]

On Wed, Feb 23, 2022 at 3:21 PM Vladimir Oltean <vladimir.oltean at nxp.com> wrote:
>
> A DM_ETH driver may use phy_connect() towards a PHY address on an MDIO
> bus which is not specified in the device tree, as evidenced by:
>
> pfe_eth_probe
> -> pfe_phy_configure
>    -> phy_connect
>
> When this happens, the PHY will have an invalid OF node.
>
> When ar803x_config() runs, it silently fails at ar803x_of_init(), and
> therefore, fails to run the rest of the initialization.
>
> This makes MII_BMCR contain what it had after BMCR_RESET (0x8000) has
> been written into it by phy_reset(). Since BMCR_RESET is volatile and
> self-clearing, the MII_BMCR ends up having a value of 0x0. The further
> configuration of this register, which is supposed to be handled by
> genphy_config_aneg() lower in ar803x_config(), never gets a chance to
> run due to this early error from ar803x_of_init().
>
> As a result of having MII_BMCR as 0, the following symptom appears:
>
> => setenv ethact pfe_eth0
> => setenv ipaddr 10.0.0.1
> => ping 10.0.0.2
> pfe_eth0 Waiting for PHY auto negotiation to complete......... TIMEOUT !
> Could not initialize PHY pfe_eth0
>
> Manually writing 0x1140 into register 0 of the PHY makes the connection
> work, but it is rather desirable that the port works without any manual
> intervention.
>
> Fixes: fe6293a80959 ("phy: atheros: add device tree bindings and config")
> Signed-off-by: Vladimir Oltean <vladimir.oltean at nxp.com>
> ---
>  drivers/net/phy/atheros.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/phy/atheros.c b/drivers/net/phy/atheros.c
> index f922fecd6b5d..fa1fe08518f4 100644
> --- a/drivers/net/phy/atheros.c
> +++ b/drivers/net/phy/atheros.c
> @@ -199,7 +199,7 @@ static int ar803x_of_init(struct phy_device *phydev)
>
>         node = phy_get_ofnode(phydev);
>         if (!ofnode_valid(node))
> -               return -EINVAL;
> +               return 0;
>
>         priv = malloc(sizeof(*priv));
>         if (!priv)
> --
> 2.25.1
>
Reviewed-by: Ramon Fried <rfried.dev at gmail.com>