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

[Heiko Schocher]

Hello Wei,

On 24.11.23 03:33, Wei Fang wrote:
>> -----Original Message-----
>> From: Andrew Lunn <andrew@xxxxxxx>
>> Sent: 2023年11月24日 4:09
>> To: Heiko Schocher <heiko.schocher@xxxxxxxxx>
>> Cc: netdev@xxxxxxxxxxxxxxx; Heiko Schocher <hs@xxxxxxx>; Clark Wang
>> <xiaoning.wang@xxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Eric
>> Dumazet <edumazet@xxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>;
>> dl-linux-imx <linux-imx@xxxxxxx>; Paolo Abeni <pabeni@xxxxxxxxxx>;
>> Shenwei Wang <shenwei.wang@xxxxxxx>; Wei Fang <wei.fang@xxxxxxx>;
>> linux-kernel@xxxxxxxxxxxxxxx
>> 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@xxxxxxx>
>>> ---
>>>
>>>  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.
>>
> Yes, there was indeed a similar patch [1] before. but this issue seems to only exist
> in downstream tree, because there is a local patch which is not in the upstream.
> 
>         /* board only enable one mii bus in default */
>         if (!of_get_property(np, "fsl,mii-exclusive", NULL))
>                 fep->quirks |= FEC_QUIRK_SINGLE_MDIO;

Yes, sorry for overseeing this ... but there are SoCs in upstream which
set FEC_QUIRK_SINGLE_MDIO and so mii bus from for example fec0 is used on
other fecX devices, correct?

And for them probing currently fail, when probed before fec0.

> I will think about how to solve this issue in downstream if I'm free later.
> 
> [1] https://lore.kernel.org/lkml/20230208101821.871269-1-alexander.sverdlin@xxxxxxxxxxx/T/#r6313852054bf12baabe21418584fbb6d58343197

Hmm.. simply deferring the probe to later point solves the problem here.

I added Alexander may he can comment...

bye,
Heiko
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