Subject: Re: [PATCH net] net: enetc: fix fallback PHY address handling and do not skip setting for addr 0

From: Alexander Stein <[email-masked]>
Date: Wed, 04 Mar 2026 14:58:18 +0100

Am Dienstag, 3. März 2026, 11:30:47 CET schrieb Wei Fang:
> The current netc_get_phy_addr() implementation falls back to PHY address
> 0 when the "mdio" node or any PHY child node is missing. On i.MX95, this
> causes failures when a real PHY is actually assigned address 0 and is
> managed through the EMDIO interface, the bit 0 of phy_mask becomes set,
> leading imx95_enetc_mdio_phyaddr_config() to return an error, and the
> netc_blk_ctrl driver probe subsequently fails. Fix this by returning
> -ENODEV when neither an "mdio" node nor any PHY node is present.
> 
> Given that some platforms may use PHY address 0 (I suppose the PHY may
> not treat address 0 as a broadcast address or default response address).
> It is possible for some boards to connect multiple PHYs to a single
> ENETC MAC, for example:
> 
>   - a SGMII PHY with a non-zero address (selected via DTS_A)
>   - a RGMII PHY with address 0 (selected via DTS_B)
> 
> For the case where the ENETC port MDIO is used to manage the PHY, when
> switching from DTS_A to DTS_B via soft reboot, LaBCR[MDIO_PHYAD_PRTAD]
> must be updated to 0 because the NETCMIX block is not reset during soft
> reboot. However, the current driver explicitly skips configuring address
> 0, which leaves the hardware in an inconsistent state.
> 
> Therefore, remove the special-case skip of PHY address 0 so that valid
> configurations using address 0 are properly supported.
> 
> Reported-by: Alexander Stein <[email-masked]>
> Closes: https://lore.kernel.org/all/7825188.GXAFRqVoOG@steina-w
> Fixes: 6633df05f3ad ("net: enetc: set the external PHY address in IERB for port MDIO usage")
> Fixes: 50bfd9c06f0f ("net: enetc: set external PHY address in IERB for i.MX94 ENETC")
> Signed-off-by: Wei Fang <[email-masked]>

Thanks,
Tested-by: Alexander Stein <[email-masked]>

> ---
>  .../ethernet/freescale/enetc/netc_blk_ctrl.c  | 24 ++++++++-----------
>  1 file changed, 10 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/netc_blk_ctrl.c b/drivers/net/ethernet/freescale/enetc/netc_blk_ctrl.c
> index 7fd39f895290..92a0f824dae7 100644
> --- a/drivers/net/ethernet/freescale/enetc/netc_blk_ctrl.c
> +++ b/drivers/net/ethernet/freescale/enetc/netc_blk_ctrl.c
> @@ -333,11 +333,13 @@ static int netc_get_phy_addr(struct device_node *np)
>  
>  	mdio_node = of_get_child_by_name(np, "mdio");
>  	if (!mdio_node)
> -		return 0;
> +		return -ENODEV;
>  
>  	phy_node = of_get_next_child(mdio_node, NULL);
> -	if (!phy_node)
> +	if (!phy_node) {
> +		err = -ENODEV;
>  		goto of_put_mdio_node;
> +	}
>  
>  	err = of_property_read_u32(phy_node, "reg", &addr);
>  	if (err)
> @@ -423,6 +425,9 @@ static int imx95_enetc_mdio_phyaddr_config(struct platform_device *pdev)
>  
>  			addr = netc_get_phy_addr(gchild);
>  			if (addr < 0) {
> +				if (addr == -ENODEV)
> +					continue;
> +
>  				dev_err(dev, "Failed to get PHY address\n");
>  				return addr;
>  			}
> @@ -433,12 +438,6 @@ static int imx95_enetc_mdio_phyaddr_config(struct platform_device *pdev)
>  				return -EINVAL;
>  			}
>  
> -			/* The default value of LaBCR[MDIO_PHYAD_PRTAD ] is
> -			 * 0, so no need to set the register.
> -			 */
> -			if (!addr)
> -				continue;
> -
>  			switch (bus_devfn) {
>  			case IMX95_ENETC0_BUS_DEVFN:
>  				netc_reg_write(priv->ierb, IERB_LBCR(0),
> @@ -578,16 +577,13 @@ static int imx94_enetc_mdio_phyaddr_config(struct netc_blk_ctrl *priv,
>  
>  	addr = netc_get_phy_addr(np);
>  	if (addr < 0) {
> +		if (addr == -ENODEV)
> +			return 0;
> +
>  		dev_err(dev, "Failed to get PHY address\n");
>  		return addr;
>  	}
>  
> -	/* The default value of LaBCR[MDIO_PHYAD_PRTAD] is 0,
> -	 * so no need to set the register.
> -	 */
> -	if (!addr)
> -		return 0;
> -
>  	if (phy_mask & BIT(addr)) {
>  		dev_err(dev,
>  			"Find same PHY address in EMDIO and ENETC node\n");
> 

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