static irqreturn_t sport_rx_isr(int irq, void *dev_id)
{
	unsigned int i, j;
	struct nortel *c = (struct nortel *)dev_id;

/*
 * iRxBuffer points to what was just received.
 * iTxBuffer points to what was just transmitted.
 * Copy the data received into the channel structure,
 * update these pointers, and copy the data to transmit.
 */
	copy_nortel_to_internal(c, iRxBuffer);

	iRxBuffer += TDM_CHANNELS;
	j = bfin_read_DMA3_START_ADDR();
	if((unsigned int)iRxBuffer >= j + DMA_BUFLEN)
		iRxBuffer = (u8 *)j;

	iTxBuffer += TDM_CHANNELS;
	j = bfin_read_DMA4_START_ADDR();
	if((unsigned int)iTxBuffer >= j + DMA_BUFLEN)
		iTxBuffer = (u8 *)j;

	copy_internal_to_nortel(c, iTxBuffer);

/*
 * The next transfer is now set up and waiting.
 * Acknowledge the transfer and let the next one go.
 */

	i = bfin_read_DMA3_IRQ_STATUS();
	j = DMA_DONE;
	if(i & DMA_ERR) {
		if(debug) printk(KERN_DEBUG "sport_rx_isr: DMA5 reported an error\n");
		j |= DMA_ERR;
		}

	bfin_write_DMA3_IRQ_STATUS(j);		/* ACK DMA (and error if present) */
	__builtin_bfin_ssync();

/*
 * We must begin to process the received frame. Right now,
 * we do this within the IRQ handler since it's fast,
 * but this is the routine that you may want to kick off to a
 * bottom-half handler (tasklet or workqueue).
 *
 * Once the frame is processed, we must do the ethernet side.
 * If we are providing sync to the PC, we kick off a TDMoE packet
 * every 8 (ZT_CHUNKSIZE) frames.
 * If we are not providing sync to the PC, we don't worry about
 * ethernet at all, as it will be taking care of by the
 * ethernet receive code.
 */

	process_frame(c);

	++c->intcount;
	if(tdmoe_master && (c->intcount % 8 == 0)) {
		copy_internal_to_tdmoe(c);			/* also queues packet for tx */
		tasklet_hi_schedule(&eth_flush_tasklet);	/* actually put the frames on the wire */
	}

	return IRQ_HANDLED;
}