Re: assert in phylink.c with lan7801 and dp83tc811 since kernel 6.18

[Andrew Lunn <andrew@lunn.ch>]

On Wed, May 06, 2026 at 03:04:42PM +0200, Maxime Chevallier wrote:
> 
> 
> On 06/05/2026 14:39, Andrew Lunn wrote:
> >> So for me it somewhere happens in phylink_validate_mac_and_pcs()
> > 
> > I was expecting to see more debug output, but reading the code, i was
> > also thinking we need to look at phylink_validate_mac_and_pcs().
> > 
> > You are going in the correct direction putting lots of printk() in the
> > code. We need to find where it returns EINVAL:
> 
> [...]
> 
> > 
> > In the end, we are probably going to find that what the MAC says its
> > capabilities are don't match what the PCS says it can do.
> > 
> > Thinking about that, it says phy mode RGMII. You generally don't use a
> > PCS with RGMII, so that is suspicious.
> > 
> 
> Another thing to consider is that in this case, we're attaching to a
> dp83tc811, so a 100BaseT1 PHY. Does the PHY driver correctly populates
> the supported features ?

Using RGMII to connect to a 100BaseT is also odd. It does happen, but
it is a bit of a corner case, and something could be going wrong here.

   Andrew