TMS320F28335: Timer problem.

I want to set a timer to count milliseconds without interrupt.

So I configure a timer (CPU frequency = 120 Mhz)

void SysTimerInit(void)
{
    Uint32 prescaler;

    // Make sure timers are stopped:
    CpuTimer1Regs.TCR.bit.TSS = 1;

    // Initialize timer period to maximum:
    CpuTimer1Regs.PRD.all  = 0xFFFFFFFF;
    
    prescaler = 120000-1;  //1000us->1ms
    CpuTimer1Regs.TPR.bit.TDDR = (prescaler & 0x0000FFFF);
    CpuTimer1Regs.TPRH.bit.TDDRH = (prescaler >> 8);

    // Initialize timer control register:
    CpuTimer1Regs.TCR.bit.TRB = 1;      // 1 = reload timer
    CpuTimer1Regs.TCR.bit.SOFT = 1;
    CpuTimer1Regs.TCR.bit.FREE = 1;     // Timer Free Run
    CpuTimer1Regs.TCR.bit.TIE = 0;      // 0 = Disable/ 1 = Enable Timer Interrupt
    CpuTimer1Regs.TCR.bit.TSS = 0;      // 1 = Stop timer, 0 = Start/Restart Timer
}

And functions to handle the counter

void SysTimerSet(Uint32 *compare_val, Uint32 count_ms)
{
    Uint32 timer_count_val = CpuTimer1Regs.TIM.all;
    *compare_val = timer_count_val - count_ms;
}

Uint16 SysTimerElapsed(Uint32 *compare_val)
{
    Uint32 timer_count_val = CpuTimer1Regs.TIM.all;
    return (timer_count_val <= *compare_val);
}

And I test.

SysTimerInit();
SysTimerSet(&compare_val, 100);

while(1)
{
   if(SysTimerElapsed(&compare_val))
   {
	SysTimerSet(&compare_val, 100);
   }
}

In the debugger I should see variable compare_val decremented by 100. But I see some random numbers. Where is my mistake?