AM3352: spi has no read clock

Hi,

   I have a problem about SPI read clock. here my code:

   u16 ,*rev_buf.

   u16 reg_addr = 16;

     tran.tx_buf = &reg_addr;
     tran.rx_buf = rev_buf;
    tran.bits_per_word = 16;
     tran.speed_hz = 2000000;
     tran.len = 2;
       
  spi_message_init(&message);
  spi_message_add_tail(&tran, &message);
    
  status = spi_sync(g_fpga_dev->spi, &message);

   if (status)
     {
        pr_info(" fpga spi_sync fail...\n");
      
     }

now  I only see the writing clock through the oscilloscope(16bit clock),but there is no read clock.so I can get reading data.it is right that it has 32 clocks.

Please give me some advice. thanks.