src/mainboard/apple/macbook21/Makefile.inc - coreboot - Gitiles

 romstage-y += gpio.c
 bootblock-y += early_init.c
 romstage-y += early_init.c

 ramstage-y += cstates.c
	romstage-y += gpio.c
	bootblock-y += early_init.c
	romstage-y += early_init.c

	ramstage-y += cstates.c