nfs mount RPC service issue

Ported a 4.1 kernel to ARMv8/CA72 board.  I always failed with the following command

# mount 10.85.151.108:/srv /mnt/nfs
[  241.430956] svc: failed to register lockdv1 RPC service (errno 111).
mount: mounting 10.85.151.108:/srv on /mnt/nfs failed: Connection refused

Finally I have to use this
# mount -o port=2049,nolock,proto=tcp 10.85.151.108:/srv /mnt/nfs

Still trying to figure out why udp is not working.