Messages in this thread | | | Date | Tue, 21 Feb 2023 10:44:44 -0800 | Subject | Re: BCM54220: After the BCM54220 closes the auto-negotiation, the configuration forces the 1000M network port to be linked down all the time. | From | Doug Berger <> |
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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
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