[coreboot] SeaBIOS does not always recognice the USB key as boot device

[Matthias Apitz]

Hello,

I have some (yes, some) Acer C720 Chromebooks which are "rooted" to
enter SeaBIOS to boot any OS from USB or SSD. This works fine, in
general.

I have one particular USB key, which says on attach to a FreeBSD system about itself:

Aug  5 20:55:13 c720-r276659 kernel: da0: <JetFlash Transcend 8GB 8.07> Removable Direct Access SCSI-4 device 
Aug  5 20:55:13 c720-r276659 kernel: da0: Serial Number KWUQE9E8
Aug  5 20:55:13 c720-r276659 kernel: da0: 40.000MB/s transfers
Aug  5 20:55:13 c720-r276659 kernel: da0: 7487MB (15335422 512 byte sectors: 255H 63S/T 954C)
Aug  5 20:55:13 c720-r276659 kernel: da0: quirks=0x12<NO_6_BYTE,NO_RC16>
Aug  5 20:55:13 c720-r276659 kernel: GEOM: da0: the secondary GPT header is not in the last LBA.
Aug  5 20:55:13 c720-r276659 kernel: GEOM: diskid/DISK-KWUQE9E8: the secondary GPT header is not in the last LBA.

This one (and only this one in all my C720) on power-on is not reliable detected
as boot device. A press on ESC only offers the internal SSD to boot from. If
it is detected (in 1 of 10 power cycles), it boots fine.

What can I do, apart of trashing the USB key?

Thanks

matthias