ethernet example in cyclone V GT kits, can't drive the TSE , help!!

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I use the ethernet example which is in the cyclone V GT installation package( cycloneVGT_5cgtfd9ef35_fpga\examples\board_update_ portal ) 

 I download the c5gt_fpga_bup.sof into cyclone V GT Development board,and then debug my simple TSE driver ,I found some problem.  1: i set the TSE into loop mode, RX_SGDMA's ISR is printing the received loopback data.  the follow datas are received loopback data,i found a problem  in first RX interrupt ,the datas are correct, but in the followed RX interrupts ,the datas are always zero ??? why???( It Looks like the SGDMA can't write correct data to receive memory)   RX descriptor reported OK 0 0 ff ff ff ff ff ff 0 1c 23 17 4a cb 8 6 0 1 8 0 6 4 0 1 0 1c 23 17 4a cb c0 a8 1 2 0 0 0 0 0 0 c0 a8 1 72 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 0 0  RX descriptor reported OK 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  RX descriptor reported OK 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  RX descriptor reported OK 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  RX descriptor reported OK 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  RX descriptor reported OK  my simple drivers:  ethernet_init(); sgdma_tx_dev = alt_avalon_sgdma_open("/dev/sgdma_tx"); sgdma_rx_dev = alt_avalon_sgdma_open("/dev/sgdma_rx"); alt_avalon_sgdma_register_callback( sgdma_rx_dev, (alt_avalon_sgdma_callback) &sgdma_rx_isr, //ALTERA_AVALON_SGDMA_CONTROL_IE_DESC_COMPLETED_MSK &#65372;  ALTERA_AVALON_SGDMA_CONTROL_IE_CHAIN_COMPLETED_MSK | ALTERA_AVALON_SGDMA_CONTROL_IE_GLOBAL_MSK  , 0); while(1){ usleep(1000000); alt_avalon_sgdma_construct_stream_to_mem_desc( &desc[10],// &desc[11],// rx_payload,// 0,// 0);//write_fixed   alt_avalon_sgdma_construct_mem_to_stream_desc( &desc[2], &desc[3], buf, 66, 0, 1,//SOP 1,//EOP 0); sgdma_rx&#21644;sgdma_tx alt_avalon_sgdma_do_async_transfer(sgdma_rx_dev, &desc[10]); usleep(100); alt_avalon_sgdma_do_sync_transfer (sgdma_tx_dev, &desc[2]);   }   void sgdma_rx_isr(void * context, u_long intnum) { int i=0; printf("RX descriptor reported OK\n"); for(i=0; i<68; i++){ printf("%x ",rx_payload); rx_payload=0x00; } printf("\n"); }