imx8mn with mv88e6320 fails to retrieve IP address

imx8mn with mv88e6320 fails to retrieve IP address

[Fabio Estevam]

Hi,

On an imx8mn-based board with a mv88e6320 switch, an IP address can be
retrieved just fine in most of the cases.

However, when using an external Trendnet switch, it is not possible to
retrieve an IP address via DHCP. Using a static IP address works fine
though.

When DHCP works, ethtool reports:

# ethtool  eth1
Settings for eth1:
Supported ports: [ TP MII ]
Supported link modes:   10baseT/Half 10baseT/Full
                        100baseT/Half 100baseT/Full
                        1000baseT/Full
Supported pause frame use: Symmetric
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes:  10baseT/Half 10baseT/Full
                        100baseT/Half 100baseT/Full
                        1000baseT/Full
Advertised pause frame use: Symmetric
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                     100baseT/Half 100baseT/Full
                                     1000baseT/Full
Link partner advertised pause frame use: No
Link partner advertised auto-negotiation: Yes
Link partner advertised FEC modes: Not reported
Speed: 1000Mb/s
Duplex: Full
Auto-negotiation: on
master-slave cfg: preferred master
master-slave status: slave
Port: MII
PHYAD: 3
Transceiver: external
Supports Wake-on: d
Wake-on: d
Link detected: yes

When the Trendnet switch is used, DHCP fails and ethtool reports just
these lines differently:

        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half 100baseT/Full
                                             1000baseT/Half 1000baseT/Full
        Link partner advertised pause frame use: Symmetric

Other PCs can retrieve IP addresses via DHCP through the Trendnet
switch correctly, but the imx8mn board fails.

Would you have any suggestions for debugging this problem?

Thanks,

Fabio Estevam

Re: imx8mn with mv88e6320 fails to retrieve IP address

[Andrew Lunn]

> When the Trendnet switch is used, DHCP fails and ethtool reports just
> these lines differently:
> 
>         Link partner advertised link modes:  10baseT/Half 10baseT/Full
>                                              100baseT/Half 100baseT/Full
>                                              1000baseT/Half 1000baseT/Full
>         Link partner advertised pause frame use: Symmetric

So all the local link modes are missing?

What does mii-tool -vvv show?

     Andrew

Re: imx8mn with mv88e6320 fails to retrieve IP address

[Andrew Lunn]

> When the Trendnet switch is used, DHCP fails and ethtool reports just
> these lines differently:
> 
>         Link partner advertised link modes:  10baseT/Half 10baseT/Full
>                                              100baseT/Half 100baseT/Full
>                                              1000baseT/Half 1000baseT/Full
>         Link partner advertised pause frame use: Symmetric

Ah, i read that wrong. What you are saying is the Trendnet additionally
has 1000BaseT/Half, and symmetric pause.

1000BaseT/Half should not be causing the problem, 1000baseT/Full will
win the election, and 1000baseT/Half is not even supported by
mv88e6xxx so is not even an option in the election.

So this is might be down to symmetric pause being negotiated.  You
might be able to prove this by hacking mv88e6185_phylink_get_caps()
and remove MAC_SYM_PAUSE. It should then no longer advertise pause,
and so the resolved auto-neg should not have pause.

    Andrew

Re: imx8mn with mv88e6320 fails to retrieve IP address

[Fabio Estevam]

Hi Andrew,

On Wed, Jun 21, 2023 at 6:43 PM Andrew Lunn <andrew@lunn.ch> wrote:

> So this is might be down to symmetric pause being negotiated.  You
> might be able to prove this by hacking mv88e6185_phylink_get_caps()
> and remove MAC_SYM_PAUSE. It should then no longer advertise pause,
> and so the resolved auto-neg should not have pause.

Thanks for your input.

Just upgraded to the latest 6.1.35 and the DHCP issue does not happen anymore.

Thanks