RE: [PATCH iwl-net v2] ixgbe: fix MDIO bus lifetime

[Loktionov, Aleksandr]

> -----Original Message-----
> From: Richard Patel <ripatel@xxxxxxx>
> Sent: Sunday, September 6, 2026 4:33 AM
> To: intel-wired-lan@xxxxxxxxxxxxxxxx
> Cc: Nguyen, Anthony L <anthony.l.nguyen@xxxxxxxxx>; Kitszel,
> Przemyslaw <przemyslaw.kitszel@xxxxxxxxx>; Andrew Lunn
> <andrew@xxxxxxx>; Steve Douthit <stephend@xxxxxxxxxxxxxxx>;
> netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Richard Patel
> <ripatel@xxxxxxx>
> Subject: [PATCH iwl-net v2] ixgbe: fix MDIO bus lifetime
> 
> Plugging in an unsupported SFP module caused ixgbe NICs to get wedged
> permanently.
> 
> ixgbe unregisters the netdev when rejecting an SFP transceiver as
> unsupported.
> 
>   ixgbe 0000:3b:00.0: failed to initialize because an unsupported SFP+
> module type was detected.
>   ixgbe 0000:3b:00.0: Reload the driver after installing a supported
> module.
>   ixgbe 0000:3b:00.0: removed PHC on enp59s0
> 
> This code path failed to unregister an MDIO bus owned by that netdev,
> so when unregister_netdev() tries to tear it down (via device_del() ->
> devres_release_all() -> mdiobus_free()), it trips over the leaked
> registration.
> 
>   ixgbe-mdio-0000:3b:00.0: not in UNREGISTERED state
>   WARNING: drivers/net/phy/mdio_bus_provider.c:711 at
> mdiobus_free+0x3d/0x50, CPU#21: kworker/u128:0/12
> 
> This prevents ixgbe from reloading, even after PCIe remove/rescan:
> 
>   sysfs: cannot create duplicate filename '/class/mdio_bus/ixgbe-mdio-
> 0000:3b:00.0'
> 
> Switch to devm_mdiobus_register(), drop custom unregister calls.
> This is safe because the bus is already devm-allocated, so unregister
> always happens before free.
> 
> Assisted-by: LLM
> Fixes: 8fa10ef01260 ("ixgbe: register a mdiobus")
> Suggested-by: Andrew Lunn <andrew@xxxxxxx>
> Signed-off-by: Richard Patel <ripatel@xxxxxxx>
> ---
> v1 -> v2: use devm_mdiobus_register() instead of another
>           mdiobus_unregister() call
> v1: https://lore.kernel.org/netdev/20260826042945.2344686-1-
> ripatel@xxxxxxx/
> 
>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 9 ++-------
> drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c  | 2 +-
>  2 files changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> index f91856498eb2..96f60269fca6 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> @@ -8471,6 +8471,7 @@ static void ixgbe_sfp_detection_subtask(struct
> ixgbe_adapter *adapter)
>  		e_dev_err("Reload the driver after installing a "
>  			  "supported module.\n");
>  		unregister_netdev(adapter->netdev);
> +		adapter->mii_bus = NULL;
>  	}
>  }
> 
> @@ -8693,11 +8694,8 @@ static void ixgbe_service_task(struct
> work_struct *work)
>  	}
>  	if (ixgbe_check_fw_error(adapter)) {
>  		if (!test_bit(__IXGBE_DOWN, &adapter->state)) {
> -			if (adapter->mii_bus) {
> -				mdiobus_unregister(adapter->mii_bus);
> -				adapter->mii_bus = NULL;
> -			}
>  			unregister_netdev(adapter->netdev);
> +			adapter->mii_bus = NULL;
>  		}
>  		ixgbe_service_event_complete(adapter);
>  		return;
> @@ -12104,9 +12102,6 @@ static void ixgbe_remove(struct pci_dev *pdev)
>  	if (adapter->hw.mac.type == ixgbe_mac_e610)
>  		ixgbe_disable_link_status_events(adapter);
> 
> -	if (adapter->mii_bus)
> -		mdiobus_unregister(adapter->mii_bus);
> -
>  #ifdef CONFIG_IXGBE_DCA
>  	if (adapter->flags & IXGBE_FLAG_DCA_ENABLED) {
>  		adapter->flags &= ~IXGBE_FLAG_DCA_ENABLED; diff --git
> a/drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c
> index ab733e73927d..74631cb2ddbc 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c
> @@ -1086,7 +1086,7 @@ int ixgbe_mii_bus_init(struct ixgbe_hw *hw)
>  	hw->phy.mdio.mode_support = MDIO_SUPPORTS_C45 |
> MDIO_SUPPORTS_C22;
> 
>  	adapter->mii_bus = bus;
> -	return mdiobus_register(bus);
> +	return devm_mdiobus_register(dev, bus);
>  }
> 
>  /**
> --
> 2.52.0


Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@xxxxxxxxx>