Problem with GPIO (P2) interrupt

Hi there,

I tried to use GPIO (P2) interrupt on TM4C1294. Codes are done on CCS

1. Interrupt handler is added to startup_ccs.c's GPIO Port P2 entry
2. MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOP) is called
3. MAP_GPIOPinTypeGPIOInput(GPIO_PORTP_BASE, GPIO_PIN_2) is called
4. IntPrioritySet(INT_GPIOP2, 0xc0);
5. IntEnable(INT_GPIOP2) and IntMasterEnable() are invoked
6. Applied to P2 is pulses with width of 50us , frequency 64Khz.

but no interrupt is generated, I got a feeling I might need to specify edge/level(?), but I can't find enough info on how to use it, but at this point, I got no interrupt.

What did I missed here?

Thanks for any pointer/reading!