Re: [PATCH v2 1/2] net: phy: microchip: add downshift tunable support for LAN88xx

[Andrew Lunn]

On Tue, Mar 31, 2026 at 12:46:26AM +0200, Nicolai Buchwitz wrote:
> Implement the standard ETHTOOL_PHY_DOWNSHIFT tunable for the LAN88xx
> PHY. This allows runtime configuration of the auto-downshift feature
> via ethtool:
> 
>   ethtool --set-phy-tunable eth0 downshift on count 3
> 
> The LAN88xx PHY supports downshifting from 1000BASE-T to 100BASE-TX
> after 2-5 failed auto-negotiation attempts. Valid count values are
> 2, 3, 4 and 5.
> 
> This is based on an earlier downstream implementation by Phil Elwell.
> 
> Signed-off-by: Nicolai Buchwitz <nb@xxxxxxxxxxx>

Reviewed-by: Andrew Lunn <andrew@xxxxxxx>

    Andrew