dm8168内核编译出错

CC [M] drivers/mtd/maps/intel_vr_nor.o
CC [M] drivers/mtd/maps/gpio-addr-flash.o
LD drivers/mtd/nand/built-in.o
CC [M] drivers/mtd/nand/nand_base.o
drivers/mtd/nand/nand_base.c: In function ‘nand_command_lp’:
drivers/mtd/nand/nand_base.c:740: error: implicit declaration of function ‘dmb’
make[3]: *** [drivers/mtd/nand/nand_base.o] Error 1
make[2]: *** [drivers/mtd/nand] Error 2
make[1]: *** [drivers/mtd] Error 2
make: *** [drivers] Error 2

内核编译时发现发现到这出错啦，这是什么情况