I can't get the 1000Mbps external loopback to work on i.MX8M eval board. The link just never comes up even though I have followed all the suggested steps and have a gigabit external loopback connected.
FYI, the internal gigabit phy loopback, which is almost identical apart from a few lines of code, works fine.
The 10Mbps and 100Mbps external loopback also work with no problem (which is also very similar code apart from one or two bits in different registers). Is there anything specific to 1000Mbps on i.MX8M? It feels like I am missing something?
The external ethernet loopback I am using is wired as per recommend wiring for the net (4 pairs connected).