mlx5 sub function issue

Hi all,
       I have some confusion with mlx5 sub function feature. I tested it 
with Mellanox ConnectX-6 Dx recently,
then I found the maximum amount of SF in each PF is just 128, I‘m not 
sure if there is a problem with
my configuration, or there are some limits of SF in ConnectX-6.
Here is the environment:
system:                    CentOS Linux release 7.9.2009
NIC:                         Mellanox Technologies MT2892 Family 
[ConnectX-6 Dx]
firmware-version:   22.29.2002 (MT_0000000430)
kernel:                    net-next master branch 
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/
mlxconfig:
PF_BAR2_ENABLE  True(1)
PF_BAR2_SIZE        8
PER_PF_NUM_SF   True(1)
PF_TOTAL_SF         65535
PF_SF_BAR_SIZE    0

When I tried to create more SF:

~# devlink port add pci/0000:b3:00.0 flavour pcisf pfnum 0 sfnum 128
devlink answers: No space left on device

Is there anything missed in configuration? Can I create more sub 
functions in ConnectX-6?

Trully yours,
avis