自己被自己绊住了，出于对无知的恐惧，总觉得是很难的一件事情。
demo board
ltp-ddt qspi_mtd_dd_rw
error：can't read superblock on /dev/mtdblock0.
under uboot
sf probe
SF: Detected s25fl256s_64k with page size 256 Bytes, erase size 64 KiB, total 32 MiB
sf erase 0 0x2000000
under kernel
256 64KB
mkfs.jffs2 -s 0x100 -e 0x10000 -r idyll/ -o jffs2.img
dd if=jffs2.img of=/dev/mtdblock0
mount -t jffs2 /dev/mtdblock0 /mnt