3559A烧写问题

已经按要求烧写了uboot，但是烧写内核是显示no devices available，请问怎么回事？

3. 烧写 u-boot

mw.b 0x44000000 0xff 0x100000;
tftp 0x44000000 u-boot-hi3559av100.bin;
nand erase 0x0 0x100000;
nand write 0x44000000 0x0 0x100000

4. 烧写内核
        setenv ipaddr 192.168.1.10;setenv serverip 192.168.1.107

   mw.b 0x44000000 0xff 0x900000;
tftp 0x44000000 uImage_hi3559av100_multi-core;
nand erase 0x100000 0x900000;
nand write 0x44000000 0x100000 0x900000

5. 烧写文件系统
   mw.b 0x44000000 0xff 0x1000000;
tftp 0x44000000 rootfs_hi3559av100_2k_4bit.yaffs2;
nand erase 0xA00000 0x1000000;
   
   nand write.yaffs 0x44000000 0xA00000 0xcd1700