Unable to Communicate with Bluetooth Module on i.MX8QXP

I am trying to bring up a Bluetooth module over HCI UART on an i.MX8QXP-based board, but I keep getting command tx timeout errors.
hciconfig -a shows hci0, but the BD address is 00:00:00:00:00:00 and the interface is DOWN.
root@kontron-samx8x:~# hciconfig -a
hci0: Type: Primary Bus: UART
BD Address: 00:00:00:00:00:00 ACL MTU: 0:0 SCO MTU: 0:0
DOWN
RX bytes:0 acl:0 sco:0 events:0 errors:0
TX bytes:12 acl:0 sco:0 commands:3 errors:0
Features: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
Packet type: DM1 DH1 HV1
Link policy:
Link mode: SLAVE ACCEPT

Tried bringing it up using:
hciconfig hci0 up
Results in:
Bluetooth: hci0: command 0x1003 tx timeout
Can't init device hci0: Connection timed out (110)

Why is hciconfig hci0 up failing with tx timeout?Any recommended debug steps for HCI UART communication?