root@fic-gta01:~$ lsof /dev/ttySAC0
root@fic-gta01:~$ cat /etc/inittab | grep SAC
#S:2345:respawn:/sbin/getty 115200 ttySAC0
#S:2345:respawn:/sbin/getty 115200 ttySAC0
root@fic-gta01:~$ echo 1 > /sys/devices/platform/gta01-pm-gsm.0/power_on
root@fic-gta01:~$ dmesg | tail -n 1
<6>gta01-pm-gsm gta01-pm-gsm.0: powering up GSM, thus disconnecting serial console
root@fic-gta01:~$ cu -l /dev/ttySAC0
Connected.