How to auto login /dev/ttyFIQ0

I want to make some auto start program output to /dev/ttyFIQ0, but as I tested, before I login on tty console, the program don’t has permition to access /dev/ttyFIQ0.
Can anyone tell me how to make uart console auto login when board startup?
Thank you!

I find the solution by modify /lib/systemd/system/serial-getty@.service
#ExecStart=-/sbin/agetty -o ‘-p – \u’ --keep-baud 115200,38400,9600 %I $TERM
ExecStart=-/sbin/agetty -a rock --noclear --keep-baud 115200,38400,9600 %I $TERM