Re: [PATCH v4] net: macb: Fix several edge cases in validate

On 10/26/21 1:46 PM, Russell King (Oracle) wrote:

On Tue, Oct 26, 2021 at 01:28:15PM -0400, Sean Anderson wrote:

quoted

Actually, according to the Zynq UltraScale+ Devices Register Reference
[1], the PCS does not support 10/100. So should SGMII even fall through
here?

[1] https://www.xilinx.com/html_docs/registers/ug1087/gem___pcs_control.html

Hmm. That brings with it fundamental question: if the PCS supports 1G
only, does it _actually_ support Cisco SGMII, or does it only support
1000base-X?

Of course, in the technical reference manual [1], they say

The line rate is 1 Gb/s as SGMII hardwired to function at 1 Gb/s only.
However, the data transfer rate can be forced down to 100 Mb/s or 10
Mb/s if the link partner is not capable.

which sounds like the normal byte-repetition of SGMII...

And they also talk about how the autonegotiation timeout and control words are different.

--Sean

[1] https://www.xilinx.com/support/documentation/user_guides/ug1085-zynq-ultrascale-trm.pdf