Jetson TX1 stops at countdown

[John Klos <john%ziaspace.com@localhost>]

I recently tried to get current running on a Jetson TX1. HEAD from three 
days ago stopped with:

> > NetBSD/evbarm EFI Boot (aarch64), Revision 1.8 (Tue Feb 19 18:17:45 UTC 
2019) (from NetBSD 8.99.34)
Press return to boot now, any other key for boot prompt
booting netbsd - starting in 5 seconds.

Then it hangs, with no response on the serial console.

I checked that the U-Boot version is the latest for the TX1 
(2016.07-g9c3b9a4), updated and tried again:

> > NetBSD/evbarm EFI Boot (aarch64), Revision 1.8 (Fri Feb 22 18:17:22 UTC 
2019) (from NetBSD 8.99.34)
Press return to boot now, any other key for boot prompt
booting netbsd - starting in 5 seconds.

Thoughts?

John