Reset Nios2 system block from reset_n

[Altera_Forum]

Sometimes it will reboot sometimes it will not, always works on power on boot. 

I'm using Quartus II v15, Cyclone IV, Nios2, DDR2 and uClinux on a custom board . I have a watchdog timer on the outside of the Qsys block. I’ve tried resetting reset_n for 10us to 5 sec.