[coreboot] How can I load SeaBIOS from GRUB with native VGA+VGA option ROM

[Iru Cai]

I read previous config files from board status, and configured my Lenovo
ThinkPad X220 with CONFIG_MAINBOARD_DO_NATIVE_VGA_INIT and
CONFIG_VGA_ROM_RUN. And according to:
http://www.coreboot.org/pipermail/coreboot/2014-July/078342.html

I added the bios.bin.elf to GRUB and vgabios.bin to CBFS. However, after I
chose SeaBIOS in GRUB, SeaBIOS was loaded and the screen became blank. I'm
not sure if there's something wrong with option ROM and SeaBIOS.