SPI Slave problem

I’m using TM4C123GH6PM, Tiva Launch Pad EK-TM4C123GXL to be more specific.

I have a SPI Master sending me commands, so I should parse the command and act accordingly.

I configure my chip as SPI Slave

void Ssi0Setup(void)
{
  // The SSI0 peripheral must be enabled for use.
  SysCtlPeripheralEnable(SYSCTL_PERIPH_SSI0);
  // For this example SSI0 is used with PortA[5:2].
  //SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
  // Configure the pin muxing for SSI0 functions on port A2, A3, A4, and A5.
  GPIOPinConfigure(GPIO_PA2_SSI0CLK);
  GPIOPinConfigure(GPIO_PA3_SSI0FSS);
  GPIOPinConfigure(GPIO_PA4_SSI0RX);
  GPIOPinConfigure(GPIO_PA5_SSI0TX);
  // Configure the GPIO settings for the SSI pins.This function also gives
  GPIOPinTypeSSI(GPIO_PORTA_BASE, GPIO_PIN_5 | GPIO_PIN_4 | GPIO_PIN_3 |
                   GPIO_PIN_2);
  SSIConfigSetExpClk(SSI0_BASE, SysCtlClockGet(), SSI_FRF_MOTO_MODE_0,
                       SSI_MODE_SLAVE, 2000000, 8);
  // Enable the SSI0 module.
  SSIEnable(SSI0_BASE);
  //enable interrupts
  SSIIntEnable(SSI0_BASE, SSI_RXFF | SSI_RXTO | SSI_RXOR );
  // Read any residual data from the SSI port.  This makes sure the receive
  // FIFOs are empty, so we don't read any unwanted junk.
  while(SSIDataGetNonBlocking(SSI0_BASE, &ssi_data_rx[0]))
    {
    }
}

int main()
{
  ClockSetup();
  GpioSetup();
  UartSetup();
  Ssi0Setup();
  //Enable processor interrupts.
  ROM_IntMasterEnable();

  //to see the chip alive
  UARTSendStr("Endat test\r");

  while(1)
  {
    if(ssi_int_flag)
    {
      ssi_int_flag = 0;
      SSIDataGet(SSI0_BASE, &ssi_data_rx[0]);
      // Since we are using 8-bit data, mask off the MSB.
      ssi_data_rx[0] &= 0x00FF;
      ssi_command = (ssi_data_rx[0] & 0x00CF);
      switch(ssi_command)
      {
        case ENC_SND_POS_VAL:
          UARTSendStr("Encoder send position values\r"); 
          Blink(1);
        break;
        case ENC_SEL_MEM_ARE:
          UARTSendStr("Selection of memory area\r"); 
          Blink(2);
        break;
        case ENC_REC_PARAM:
          UARTSendStr("Encoder receive parameter\r"); 
          Blink(3);
        break;
        case ENC_SND_PARAM:
          UARTSendStr("Encoder send parameter\r"); 
          Blink(4);
        break;
        case ENC_REC_RST:
          UARTSendStr("Encoder receive reset\r"); 
          Blink(5);
        break;
        default:
          UARTSendStr("Invalid command\r");  
        break;
        
      }
      //clear FIFO
      while(SSIDataGetNonBlocking(SSI0_BASE, &ssi_data_rx[0]))
      {  }
    }  
  }
}

//Interrupt for SSI0
void SSI0_ISR(void)
{
  UARTSendStr("SSI Int\r"); //for debug 
  uint32_t int_status;
  //Get the interrrupt status.
  int_status = ROM_SSIIntStatus(SSI0_BASE, true);
  // Clear the asserted interrupts.
  ROM_SSIIntClear(SSI0_BASE, int_status);
    if(int_status==SSI_RXFF)
    {
      ssi_int_flag = 1;
    }
}

I get no interrupt also i see valid signal on SSI0Rx and SSI0CLK lines.