Re: [PATCH net v2] net: dpaa: fix mode setting

[Sean Anderson <sean.anderson@linux.dev>]

On 7/17/26 08:57, Michael Walle wrote:
> On Fri Jul 17, 2026 at 2:44 PM CEST, Paolo Abeni wrote:
>> On 7/17/26 2:05 PM, Sean Anderson wrote:
>>> On 7/17/26 07:11, Paolo Abeni wrote:
>>>> On 7/17/26 12:13 PM, Michael Walle wrote:
>>>>> I've seen that, but.. that was the actual change between v1 and v2
>>>>> as suggested by Sean. It does not depend on the actual link speed,
>>>>> but the maximum link speed. So it is not relevant if the link
>>>>> negotiates to a slower speed or not. At least that now matches the
>>>>> behavior prior to the phylink conversion. If that was working -
>>>>> that I can't tell you.
>>>>
>>>> I'm sorry, following all cross revision discussion is a bit hard here.
>>>>
>>>> I don't understand if the 'link never established' is specific of your
>>>> board, or it a constant with this driver. Could you please clarify?
> 
> I don't think it's related to my board, but rather to the link being
> a SGMII one on my board. I assume Sean had an RGMII link while
> converting the driver (?) and moreover, that it worked correctly
> there :)

I didn't have a link at all! I only personally tested this conversion on
layerscape (memac). I'm pleased to learn that there were only two major
bugs, but a little concerned that it took four years to discover one of them.

>>> I think we should set byte/nibble mode in link_up as well as mac_config. That
>>> should fix the problem where the link never comes up (possibly broken since
>>> the phylink conversion). I think it's unlikely that this config is supposed
>>> to match the phy interface speed and not the link speed, but you never know...
>> FTR, the above does not answer my question ;)
>>
>> Still I think (mostly guess) bringing the mode initialization in both
>> link_up and mac_config should be safer (that is, I agree with the above
>> plan).
> 
> I agree. I looked at the original driver and there adjust_link()
> will also select between byte and nibble mode. I'll prepare a v3.
> 
> Sorry, I misunderstood Sean's intention/suggestion, thanks for
> pushing on this. FWIW, I also tried with nibble mode as the initial
> configuration on my board and link_up() is getting called. Whereas
> if it's 0 (as in being documented as "reserved", though it's the
> default), .link_up() is never called. Thus, it seems that it just
> has to be any valid setting until link_up() will set the correct
> value.
> 
> -michael