[PATCH v2] net: mtk_sgmii: implement mtk_pcs_ops

[Russell King (Oracle)]

On Mon, Jan 16, 2023 at 02:08:30PM +0100, Bjørn Mork wrote:
> Frank Wunderlich <frank-w at public-files.de> 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.

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