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Date:   Fri, 25 Nov 2022 15:36:00 +0100
From:   Maciej Fijalkowski <maciej.fijalkowski@intel.com>
To:     Zhang Changzhong <zhangchangzhong@huawei.com>
CC:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Grygorii Strashko <grygorii.strashko@ti.com>,
        "Jesse Brandeburg" <jesse.brandeburg@intel.com>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net] net: ethernet: ti: am65-cpsw: fix error handling in
 am65_cpsw_nuss_probe()
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References: <1669258989-18277-1-git-send-email-zhangchangzhong@huawei.com>
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On Thu, Nov 24, 2022 at 11:03:08AM +0800, Zhang Changzhong wrote:
> The am65_cpsw_nuss_cleanup_ndev() function calls unregister_netdev()
> even if register_netdev() fails, which triggers WARN_ON(1) in

If this has been only compile tested then I assume you haven't encounter
this WARN_ON(1) trigger by yourself?

> unregister_netdevice_many(). To fix it, make sure that
> unregister_netdev() is called only on registered netdev.
> 
> Compile tested only.
> 
> Fixes: 84b4aa493249 ("net: ethernet: ti: am65-cpsw: add multi port support in mac-only mode")
> Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
> ---
>  drivers/net/ethernet/ti/am65-cpsw-nuss.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> index c50b137..d04a239 100644
> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> @@ -2082,7 +2082,7 @@ static void am65_cpsw_nuss_cleanup_ndev(struct am65_cpsw_common *common)
>  
>  	for (i = 0; i < common->port_num; i++) {
>  		port = &common->ports[i];
> -		if (port->ndev)
> +		if (port->ndev && port->ndev->reg_state == NETREG_REGISTERED)
>  			unregister_netdev(port->ndev);

It seems that if am65_cpsw_nuss_register_ndevs() fails on
register_netdev() port->ndev is still a valid pointer, so your assumption
looks correct to me.

Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

>  	}
>  }
> -- 
> 2.9.5
>