OMAP-L138 GPIO peripheral Clock

if my question is not clear, here  what i faced exactly.

I'm working on DSP (C6748).

i have configured GP7[9] as interrupt source (input pin)  to accept clock cycles with period 3300 nanoseconds [Logic 1 period is 320 ns and logic 0 period is 2.9us]

DSP detects interrupt on Rising Edge and the ISR is as follows :

if(GPIOPinIntStatus(SOC_GPIO_0_REGS,GPIO7P9)) 
{

count++; // count no of  times ISR is executed  
GPIOPinIntClear(SOC_GPIO_0_REGS, GPIO7P9);
}

The problem is

        i have 52 clock cycles each 3300 nanoseconds coming on GP7[9] so that DSP should detects 52 interrupt (which is not the case i have )

        The DSP detects only 50 interrupt so i thought the problem is in GPIO peripheral clock .   

        So i want to know if the problem in GPIO peripheral clock or in something else ? and how to solve it ?

thanks in advance .