Re: [PATCH v2] net: mtk_sgmii: implement mtk_pcs_ops

[Bjørn Mork]

"Russell King (Oracle)" <linux@xxxxxxxxxxxxxxx> writes:
> On Mon, Jan 16, 2023 at 02:08:30PM +0100, Bjørn Mork wrote:
>> Frank Wunderlich <frank-w@xxxxxxxxxxxxxxx> writes:
>> 
>> > apart from this little problem it works much better than it actually is so imho more
>> > people should test it on different platforms.
>> 
>> Hello!  I've been banging my head against an MT7986 board with two
>> Maxlinear GPY211C phys for a while. One of those phys is connected to
>> port 5 of the MT7531 switch.  This is working perfectly.
>> 
>> The other GPY211C is connected to the second MT7986 mac.  This one is
>> giving me a headache...
>> 
>> I can only get the port to work at 2500Mb/s.  Changing the speed to
>> anything lower looks fine in ethtool etc, but traffic is blocked.
>
> My guess would be that the GPY PHY is using in-band SGMII negotiation
> (it sets VSPEC1_SGMII_ANEN_ANRS when entering SGMII mode and clears
> it in 2500base-X), but as the link is not using in-band mode on the
> PCS side, the PHY never sees its in-band negotiation complete, so the
> link between PCS and PHY never comes up.
>
> Both sides need to agree on that detail.

Any hints on how I would go about doing that?  I am a little lost here,
changing arbitrary bits I don't understand the meaning of.


Bjørn