Re: BCM54220: After the BCM54220 closes the auto-negotiation, the configuration forces the 1000M network port to be linked down all the time.

Doug Berger
2023-02-21T18:46:01Z

On 2/17/2023 12:06 AM, Wang, Xiaolei wrote:
> hi
>
> When I use the nxp-imx7 board, eth0 is connected to the PC, eth0 is turned off the auto-negotiation mode, and the configuration is forced to 10M, 100M, 1000M. When configured to force 1000M，
> The link status of phy status reg(0x1) is always 0, and the chip of phy is BCM54220, but I did not find the relevant datasheet on BCM official website, does anyone have any suggestions or the datasheet of BCM54220?
>
> thanks
> xiaolei
>
It is my understanding that the 1000BASE-T PHY requires peers to take on
asymmetric roles and that establishment of these roles requires
negotiation which occurs during auto-negotiation. Some PHYs may allow
manual programming of these roles, but it is not standardized and tools
like ethtool do not support manual specification of such details.

Therefore manual configuration of a 1000BASE-T link cannot be assumed to
work. If you want to "force" a gigabit link you should keep
auto-negotiation on and only advertise support for the speed you want.

Regards,

Doug