NFS方式启动TQ210的Android 4.0.4系统出错

使用NFS方式启动Android开发板，出现下面的错误：

dm9000 dm9000: eth0: link down

ADDRCONF(NETDEV_UP): eth0: link is notready

ADDRCONF(NETDEV_CHANGE): eth0: link becomesready

IP-Config: Complete:

    device=eth0, addr=192.168.120.186, mask=255.255.255.0,gw=255.255.255.255,

    host=192.168.120.186, domain=, nis-domain=(none),

     bootserver=192.168.120.208,rootserver=192.168.120.186, rootpath=

dm9000 dm9000: eth0: link up, 100Mbps,full-duplex, lpa 0xCDE1

VFS: Unable to mount root fs via NFS,trying floppy.

List of all partitions:

1f00            1024 mtdblock0  (driver?)

1f01           2048 mtdblock1  (driver?)

1f02            5120 mtdblock2  (driver?)

1f03        1038336 mtdblock3  (driver?)

No filesystem could mount root, tried:  nfs

Kernel panic - not syncing: VFS: Unable tomount root fs on unknown-block(2,0)

主机ＮＦＳ配置没问题，开发板从Nand启动后可以mount上NFS。下面是u-boot环境变量，请问是什么原因呢？

bootcmd=nand read.jffs2 0xc0008000 kernel;bootm 0xc0008000
netmask=255.255.255.0
gatewayip=192.168.120.254
serverip=192.168.120.186
ipaddr=192.168.120.208
bootargs=root=/dev/nfs rw rootfstype=nfs nfsroot=192.168.120.186:/home/zcw/rootfs_dir/ ip=192.168.120.186:192.168.120.208::255.255.255.0::eth0:off  init=/init console=ttySAC0,115200

已解决，参数错误，使用下面的。
bootargs=noinitrd init=/initconsole=ttySAC0 root=/dev/nfs nfsroot=192.168.120.186:/home/zcw/rootfs_dirip=192.168.120.208:192.168.120.186:192.168.120.208:255.255.255.0:::eth0:off