e1000 forced 1G support?

[Morten Brørup]

> From: Bly, Mike [mailto:mbly at ciena.com] 
> Sent: Friday, 11 February 2022 02.30
> 
> Hello,
>
> This is in regards to the DPDK E1000 driver used for the i350 [8086:1521] NIC.
>
> I am looking to see if we can get forced speed == 1000Mb (1Gb) support working on this NIC. The current DPDK driver does not appear to have support for forcing the NIC to 1G (1000M) speed. It only supports setting 100M and 10M. Is there a reason for this? Refer to: e1000_phy_force_speed_duplex_setup() in drivers/net/e1000/base/e1000_phy.c.
>
> Based on my reading of ethernet-controller-i350-datasheet.pdf it would seem we should be able to force the speed to 1G. However, even after "updating" the above mentioned function to try and support a 1G forced speed, the only way we can get two of these NICs to link up to each other at 1G, is to set the port to auto-neg. We can certainly force speed on one link to 100M or 10M and the other NIC will link up, but no luck for 1G, regardless of whether we have one or both sides in a forced speed vs. auto-neg mode.
>
> Is there a limitation I missed in the PDF perhaps?

Hi Mike,

Auto-negotiation is a *requirement* for 1 Gbps according to the IEEE 802.3 Ethernet standard, so the way to force 1 Gbps is: Enable auto-negotiation and only advertise 1 Gbps.

In other words: You cannot establish a 1 Gbps link without auto-neg.


Med venlig hilsen / Kind regards,
-Morten Brørup