编译通不过
arch/arm/cpu/armv7/start.o: In function `nand_boot_210':
/root/tiny210-u-boot-version3.1/arch/arm/cpu/armv7/start.S:229: undefined reference to `board_init_f_nand'
make[1]: *** [/root/tiny210-u-boot-version3.1/spl/u-boot-spl] Error 1
make[1]: Leaving directory `/root/tiny210-u-boot-version3.1/spl'
make: *** [spl/u-boot-spl.bin] Error 2