Coreboot + GRUB2 + xhci (baytrail_fsp)

[dgim]

Hello!
I try to startup linux from usb stick on my board (SoC e38xx, fsp_baytrail) via "Coreboot + GRUB2".
Can GRUB2 work with xhci device?
libpayload can work with xhci. How can i configure GRUB2 to use custom libpayload?

Many thank's for help.
Best regards, Jim