Re: [PATCH net] net: phy: dp83869: Set auto mdix bit for forced 100Base-Tx mode

[Malladi, Meghana]

Hi Andrew,

On 2/12/2026 6:36 PM, Andrew Lunn wrote:
> > > What about when you change the configuration out of forced 100 Full?
> > > Shouldn't the configuration be returned to how the user wants
> > > auto-MDIX configured? Should you disable robust Auto-MDIX so that
> > > "unreliable Auto-MDIX" is used?
> >
> > This bit is only necessary if link partners are configured to operational
> > modes that not supported by normal Auto MDI/MDIX mode (when one of that link
> > partners are in Forced 100Base-TX), will fix it in v2.
>
> Does this bit have any effect on normal Auto MDI/MDIX mode? Can this
> bit be set once during probe, rather than for a specific link mode?
>
> Is there an errata for this behaviour/fix? If there is please
> reference the number/document etc.

I checked with the PHY team and they pointed me to this section of the 
DP83867 datasheet[1]: 7.6.25 Configuration Register 3 (CFG3) and said 
something similar is needed for DP83869 as well. There are a lot of 
similar corner cases which they haven't tested and once done, more 
details w.r.t to the possible errata will be published in the next 
datasheet revision (aimed in the next quarter). I guess it makes more 
sense to post this fix later with the published errata.

[1]: https://www.ti.com/lit/ds/symlink/dp83867ir.pdf

> Since this is a fix, please add a Fixes: tag.
>
>      Andrew

--
Thanks,
Meghana Malladi