omapl138 linux interrupt

I have write a kernel module, it is as follow, I want it can respond DSP's interrupt.

#define REG_CHIPSIG       0x01C14174
#define REG_CHIPINT_CLEAR 0x01C14178
int i=0;
unsigned int reg_chipsig_clear;
unsigned int reg_chipsig;
static irqreturn_t handler_chipint0(int irq,void *dev_id)
{
 //clear interrupt
 writel(0x1,reg_chipsig_clear);
 //memery interrupt time
 i++;
 return IRQ_HANDLED;
   }
 

int porc_init(void)
{
 
  int result;
  printk("\nporc_init:enter\n");

  reg_chipsig=(unsigned int*)ioremap_nocache(REG_CHIPSIG,4);
  reg_chipsig_clear=(unsigned int*)ioremap_nocache(REG_CHIPINT_CLEAR,4);

  if(request_irq(IRQ_DA8XX_CHIPINT0, handler_chipint0,0,"proc_chipint0",0))
  {
   printk("porc_init:request handler_chipint0 error\n");
  } 
  printk("\nporc_init:exit\n");
  return 0;

}

void porc_exit(void)
{
  
 printk("\nporc_exit:enter\n");
 
 //get time of interrupt
 printk("i=%d\n",i);
 
 free_irq(IRQ_DA8XX_CHIPINT0,0); 
    printk("\nporc_exit:exit\n");
}
MODULE_AUTHOR("test");
MODULE_LICENSE("Dual BSD/GPL");

module_init(porc_init);
module_exit(porc_exit);

But I find that when DSP set bit0 of reg CHIPSIG the ISR will run three times, why?

I use OMAPL138.