Kurlon
I tested your suggestion fw-setenv usb_scan_1 usb=0:1 dev=sdb1, and it does work as predicted:
- when USB and SATA both hooked on, GFN boots from USB (not SATA) ++
- when SATA is disconnected, GFN hangs, unless the var is reverted beforehand or afterwards in Netconsole & Serial
Thanks again, its the 1st time a working solution was suggested for this problem with ArchLinux setup unchanged. Its simpler than adding uInitrd, but risky for an average user long term. The question now is, is that possible to add some flexibility here by further modding the Uboot env to make sure it can also boot from USB when SATA is disconnected without changing Uboot env?