Connection timed out of UART interface BT module

Hello,

I try to connect to BT module using UART interface on the latest snapshots of OE-RPB of Dragonboard 410c [link]

First, I disable the serial-getty service and reboot

$ systemctl mask serial-getty@ttyMSM0.service
$ reboot

After reboot, I try to hciconfig up, as follows:

But it shows “Connection timed out”.

The way is work on Debian-17.04 and rpb-16.09

Do you have any advice ?

Thank you