src/mainboard/google/brya/variants/baseboard/nissa/Makefile.inc - coreboot - Gitiles

 bootblock-y += gpio.c

 romstage-y += memory.c
 romstage-y += gpio.c

 ramstage-y += gpio.c
 ramstage-y += ramstage.c

 smm-$(CONFIG_SMMSTORE) += gpio.c
	bootblock-y += gpio.c

	romstage-y += memory.c
	romstage-y += gpio.c

	ramstage-y += gpio.c
	ramstage-y += ramstage.c

	smm-$(CONFIG_SMMSTORE) += gpio.c