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.

Assembly in DS-5 script

set var $AARCH64::$Core::$X0 = 0xd0020000
set var $AARCH64::$Core::$X1 = 0x609
assemble 0x00002000 A64
STR x1, [x0]
ADD x0, x0, #8
STR x1, [x0]
DSB     SY
TLBI    ALLE3
ISB
NOP
B {PC}-4
end