Microchip driver for LAN7800 does not auto-negotiate

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux (RHEL) 9
  • USB NIC LAN78xx

Issue

  • When speed and duplex are hard-set on the switch, NIC link speed/duplex is inconsistent

Resolution

Red Hat investigated this issue in bug report 34926 and delivered a fix in RHEL-9.2.0.z/kernel-5.14.0-284.67.1.el9_2 through errata RHSA-2024:3461 - Security Advisory

If this issue still occurs in your environment after updating, open a support case in the Red Hat Customer Portal referring to this solution.

Diagnostic Steps

Set the speed and duplex on the switch:

switch# speed 100 duplex full autoneg off

Check the speed with ethtool.

rhel_server# ethtool enp0s20f0u1u3


Settings for enp0s20f0u1u3:
        Supported ports: [ TP    MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supported pause frame use: Symmetric Receive-only
        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: No
        Advertised FEC modes: Not reported
        Speed: 100Mb/s
        Duplex: Half  <<<===
        Auto-negotiation: off
        master-slave cfg: preferred slave
        master-slave status: master
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        MDI-X: Unknown
        Supports Wake-on: pumbag
        Wake-on: g
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes

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