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

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Message-ID: <1af63dea-e333-cef7-2bc6-bbf4eb8c3881@denx.de>
Date:   Thu, 23 Nov 2023 16:26:18 +0100
From:   Heiko Schocher <hs@...x.de>
To:     Alexander Stein <alexander.stein@...tq-group.com>,
        netdev@...r.kernel.org, Heiko Schocher <heiko.schocher@...il.com>
Cc:     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

Hello Alexander,

On 23.11.23 16:11, Alexander Stein wrote:
> Hello Heiko,
> 
> Am Donnerstag, 23. November 2023, 14:27:43 CET schrieb Heiko Schocher:
>> 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.
> 
> But FEC_QUIRK_SINGLE_MDIO is only set for imx28. How is this related to 
> imx8qxp?

Ah, yes ... customer uses NXP based kernel there is:

        /* board only enable one mii bus in default */
        if (!of_get_property(np, "fsl,mii-exclusive", NULL))
                fep->quirks |= FEC_QUIRK_SINGLE_MDIO;

which is missing in mainline... nevertheless patch fixes a problem
with boards having quirk FEC_QUIRK_SINGLE_MDIO set.

> Will this also help for imx6ul when fec1 is almost always probed before fec0 
> due to order of DT nodes?

Yep, I think so...  do you have the chance to test such a setup?

bye,
Heiko
> 
> Best regards,
> Alexander
> 
>> 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;
>>  	}
>>
>>  	bus_freq = 2500000; /* 2.5MHz by default */
> 
> 

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