netdev - Re: [PATCH] net: fec: fix probing of fec1 when fec0 is not probed yet

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Message-ID: <132aca53-6570-41a4-b2b2-0907d74f9b31@lunn.ch>
Date: Thu, 23 Nov 2023 21:09:25 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Heiko Schocher <heiko.schocher@...il.com>
Cc: netdev@...r.kernel.org, Heiko Schocher <hs@...x.de>,
	Clark Wang <xiaoning.wang@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	NXP Linux Team <linux-imx@....com>, Paolo Abeni <pabeni@...hat.com>,
	Shenwei Wang <shenwei.wang@....com>, Wei Fang <wei.fang@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: fec: fix probing of fec1 when fec0 is not probed yet

On Thu, Nov 23, 2023 at 02:27:43PM +0100, Heiko Schocher wrote:
> it is possible that fec1 is probed before fec0. On SoCs
> with FEC_QUIRK_SINGLE_MDIO set (which means fec1 uses mii
> from fec0) init of mii fails for fec1 when fec0 is not yet
> probed, as fec0 setups mii bus. In this case fec_enet_mii_init
> for fec1 returns with -ENODEV, and so fec1 never comes up.
> 
> Return here with -EPROBE_DEFER so interface gets later
> probed again.
> 
> Found this on imx8qxp based board, using 2 ethernet interfaces,
> and from time to time, fec1 interface came not up.
> 
> Signed-off-by: Heiko Schocher <hs@...x.de>
> ---
> 
>  drivers/net/ethernet/freescale/fec_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index c3b7694a7485..d956f95e7a65 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -2445,7 +2445,7 @@ static int fec_enet_mii_init(struct platform_device *pdev)
>  			mii_cnt++;
>  			return 0;
>  		}
> -		return -ENOENT;
> +		return -EPROBE_DEFER;

I think this has been tried before.

Are there any issues with the mii_cnt++; I thought the previous
attempt as this had problems with the wrong mdio bus being assigned to
fep->mii_bus ? But i could be remembering wrongly.

	Andrew