On Mon, Mar 30, 2026 at 12:42:00AM +0200, Nicolai Buchwitz wrote:

Enable auto-downshift from 1000BASE-T to 100BASE-TX after 2 failed
auto-negotiation attempts by default. This ensures that links with
faulty or missing cable pairs (C and D) fall back to 100Mbps without
requiring userspace configuration.

Users can override or disable downshift at runtime:

  ethtool --set-phy-tunable eth0 downshift off

Signed-off-by: Nicolai Buchwitz <redacted>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew