SPI slave using EDMA3 (C6748 platform)

Hi, There is the source code in my project.

main function:

spi_setup(DEFAULT_SPI_BUS, DEFAULT_SPI_CS, DEFAULT_SPI_MODE, NULL);  //setup spi0 (slave mode) cs=2

IntRegister(C674X_MASK_INT4, spi_edma3_com_isr);
IntRegister(C674X_MASK_INT5, spi_edma3_err_isr);

IntEventMap(C674X_MASK_INT4, SYS_INT_EDMA3_0_CC0_INT1);
IntEventMap(C674X_MASK_INT5, SYS_INT_EDMA3_0_CC0_ERRINT);

IntEnable(C674X_MASK_INT4);
IntEnable(C674X_MASK_INT5);

/* Request DMA Channel and TCC for SPI Transmit*/
EDMA3RequestChannel(SOC_EDMA30CC_0_REGS, EDMA3_CHANNEL_TYPE_DMA, \
EDMA3_CHA_SPI0_TX, EDMA3_CHA_SPI0_TX, 0);

/* Request DMA Channel and TCC for SPI Receive*/
EDMA3RequestChannel(SOC_EDMA30CC_0_REGS, EDMA3_CHANNEL_TYPE_DMA, \
EDMA3_CHA_SPI0_RX, EDMA3_CHA_SPI0_RX, 0);

/* Registering Callback Function for Transmission. */
cb_Fxn[EDMA3_CHA_SPI0_TX] = &spi_edma_callback;
/* Registering Callback Function for Reception. */
cb_Fxn[EDMA3_CHA_SPI0_RX] = &spi_edma_callback;

 //set the PaRAM entries of EDMA3 for the Receive Channel of SPI0.   disable tx

spi_edma_rx((unsigned char *)dma_rx, 8);

spi_int_enable(spi, SPI_DMA_REQUEST_ENA_INT);

*************************************************************************************************************

spi_edma3_com_isr:     //spi_edma_callback

static void spi_edma_callback(unsigned int tccnum, unsigned int status)
{

if(tccnum == EDMA3_CHA_SPI0_TX)
{
EDMA3DisableTransfer(SOC_EDMA30CC_0_REGS, EDMA3_CHA_SPI0_TX, EDMA3_TRIG_MODE_EVENT);

spi_edma_rx((unsigned char *)dma_rx, 8);

}

}
else if(tccnum == EDMA3_CHA_SPI0_RX)
{
EDMA3DisableTransfer(SOC_EDMA30CC_0_REGS, EDMA3_CHA_SPI0_RX, EDMA3_TRIG_MODE_EVENT);

spi_edma_tx(data, 8);

}
}

It works fine when I just used edma for receiveing. After I used "EDMA3DisableTransfer" to disable rx and used "EDMA3EnableTransfer" to enable tx, it works fine too. But the C6748 will receive 3 extra bytes after I used "EDMA3DisableTransfer" to disable tx dma and used "EDMA3EnableTransfer" to enable rx dma,.

For example:

Master send: 0xa8 0xb8 0x00 0x11 0x22 0x45 0x55 0x90

slave receive: 0xa8 0x00 0x00 0xa8 0xb8 0x00 0x11 0x22       0x45 0x55 0x90(this 3 bytes will be lost)

The "0xa8 0x00 0x00" were not transmited by the master. Is there any problem in my code?