* Patch by Peter Ryser, 20 Feb 2004:

  Add support for the Xilinx ML300 platform

* Patch by Stephan Linz, 17 Feb 2004:
  Fix watchdog support for NIOS

* Patch by Josh Fryman, 16 Feb 2004:
  Fix byte-swapping for cfi_flash.c for different bus widths

* Patch by Jon Diekema, 14 Jeb 2004:
  Remove duplicate "FPGA Support" notes from the README file

1 files changed, 1344 insertions, 0 deletions

diff --git a/board/xilinx/xilinx_enet/xemac_intr_dma.c b/board/xilinx/xilinx_enet/xemac_intr_dma.c
new file mode 100644
index 000000000..567abb42a
--- /dev/null
+++ b/board/xilinx/xilinx_enet/xemac_intr_dma.c
@@ -0,0 +1,1344 @@
+/******************************************************************************
+*
+*     Author: Xilinx, Inc.
+*
+*
+*     This program is free software; you can redistribute it and/or modify it
+*     under the terms of the GNU General Public License as published by the
+*     Free Software Foundation; either version 2 of the License, or (at your
+*     option) any later version.
+*
+*
+*     XILINX IS PROVIDING THIS DESIGN, CODE, OR INFORMATION "AS IS" AS A
+*     COURTESY TO YOU. BY PROVIDING THIS DESIGN, CODE, OR INFORMATION AS
+*     ONE POSSIBLE IMPLEMENTATION OF THIS FEATURE, APPLICATION OR STANDARD,
+*     XILINX IS MAKING NO REPRESENTATION THAT THIS IMPLEMENTATION IS FREE
+*     FROM ANY CLAIMS OF INFRINGEMENT, AND YOU ARE RESPONSIBLE FOR OBTAINING
+*     ANY THIRD PARTY RIGHTS YOU MAY REQUIRE FOR YOUR IMPLEMENTATION.
+*     XILINX EXPRESSLY DISCLAIMS ANY WARRANTY WHATSOEVER WITH RESPECT TO
+*     THE ADEQUACY OF THE IMPLEMENTATION, INCLUDING BUT NOT LIMITED TO ANY
+*     WARRANTIES OR REPRESENTATIONS THAT THIS IMPLEMENTATION IS FREE FROM
+*     CLAIMS OF INFRINGEMENT, IMPLIED WARRANTIES OF MERCHANTABILITY AND
+*     FITNESS FOR A PARTICULAR PURPOSE.
+*
+*
+*     Xilinx hardware products are not intended for use in life support
+*     appliances, devices, or systems. Use in such applications is
+*     expressly prohibited.
+*
+*
+*     (c) Copyright 2002-2004 Xilinx Inc.
+*     All rights reserved.
+*
+*
+*     You should have received a copy of the GNU General Public License along
+*     with this program; if not, write to the Free Software Foundation, Inc.,
+*     675 Mass Ave, Cambridge, MA 02139, USA.
+*
+******************************************************************************/
+/*****************************************************************************/
+/**
+*
+* @file xemac_intr_dma.c
+*
+* Contains functions used in interrupt mode when configured with scatter-gather
+* DMA.
+*
+* The interrupt handler, XEmac_IntrHandlerDma(), must be connected by the user
+* to the interrupt controller.
+*
+* <pre>
+* MODIFICATION HISTORY:
+*
+* Ver   Who  Date     Changes
+* ----- ---- -------- ---------------------------------------------------------
+* 1.00a rpm  07/31/01 First release
+* 1.00b rpm  02/20/02 Repartitioned files and functions
+* 1.00c rpm  12/05/02 New version includes support for simple DMA and the delay
+*                     argument to SgSend
+* 1.00c rpm  02/03/03 The XST_DMA_SG_COUNT_EXCEEDED return code was removed
+*                     from SetPktThreshold in the internal DMA driver. Also
+*                     avoided compiler warnings by initializing Result in the
+*                     interrupt service routines.
+* 1.00c rpm  03/26/03 Fixed a problem in the interrupt service routines where
+*                     the interrupt status was toggled clear after a call to
+*                     ErrorHandler, but if ErrorHandler reset the device the
+*                     toggle actually asserted the interrupt because the
+*                     reset had cleared it.
+* </pre>
+*
+******************************************************************************/
+
+/***************************** Include Files *********************************/
+
+#include "xbasic_types.h"
+#include "xemac_i.h"
+#include "xio.h"
+#include "xbuf_descriptor.h"
+#include "xdma_channel.h"
+#include "xipif_v1_23_b.h"	/* Uses v1.23b of the IPIF */
+
+/************************** Constant Definitions *****************************/
+
+/**************************** Type Definitions *******************************/
+
+/***************** Macros (Inline Functions) Definitions *********************/
+
+/************************** Variable Definitions *****************************/
+
+/************************** Function Prototypes ******************************/
+
+static void HandleDmaRecvIntr(XEmac * InstancePtr);
+static void HandleDmaSendIntr(XEmac * InstancePtr);
+static void HandleEmacDmaIntr(XEmac * InstancePtr);
+
+/*****************************************************************************/
+/**
+*
+* Send an Ethernet frame using scatter-gather DMA. The caller attaches the
+* frame to one or more buffer descriptors, then calls this function once for
+* each descriptor. The caller is responsible for allocating and setting up the
+* descriptor. An entire Ethernet frame may or may not be contained within one
+* descriptor.  This function simply inserts the descriptor into the scatter-
+* gather engine's transmit list. The caller is responsible for providing mutual
+* exclusion to guarantee that a frame is contiguous in the transmit list. The
+* buffer attached to the descriptor must be word-aligned.
+*
+* The driver updates the descriptor with the device control register before
+* being inserted into the transmit list.  If this is the last descriptor in
+* the frame, the inserts are committed, which means the descriptors for this
+* frame are now available for transmission.
+*
+* It is assumed that the upper layer software supplies a correctly formatted
+* Ethernet frame, including the destination and source addresses, the
+* type/length field, and the data field.  It is also assumed that upper layer
+* software does not append FCS at the end of the frame.
+*
+* The buffer attached to the descriptor must be word-aligned on the front end.
+*
+* This call is non-blocking.  Notification of error or successful transmission
+* is done asynchronously through the send or error callback function.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param BdPtr is the address of a descriptor to be inserted into the transmit
+*        ring.
+* @param Delay indicates whether to start the scatter-gather DMA channel
+*        immediately, or whether to wait. This allows the user to build up a
+*        list of more than one descriptor before starting the transmission of
+*        the packets, which allows the application to keep up with DMA and have
+*        a constant stream of frames being transmitted. Use XEM_SGDMA_NODELAY or
+*        XEM_SGDMA_DELAY, defined in xemac.h, as the value of this argument. If
+*        the user chooses to delay and build a list, the user must call this
+*        function with the XEM_SGDMA_NODELAY option or call XEmac_Start() to
+*        kick off the tranmissions.
+*
+* @return
+*
+* - XST_SUCCESS if the buffer was successfull sent
+* - XST_DEVICE_IS_STOPPED if the Ethernet MAC has not been started yet
+* - XST_NOT_SGDMA if the device is not in scatter-gather DMA mode
+* - XST_DMA_SG_LIST_FULL if the descriptor list for the DMA channel is full
+* - XST_DMA_SG_BD_LOCKED if the DMA channel cannot insert the descriptor into
+*   the list because a locked descriptor exists at the insert point
+* - XST_DMA_SG_NOTHING_TO_COMMIT if even after inserting a descriptor into the
+*   list, the DMA channel believes there are no new descriptors to commit. If
+*   this is ever encountered, there is likely a thread mutual exclusion problem
+*   on transmit.
+*
+* @note
+*
+* This function is not thread-safe. The user must provide mutually exclusive
+* access to this function if there are to be multiple threads that can call it.
+*
+* @internal
+*
+* A status that should never be returned from this function, although
+* the code is set up to handle it, is XST_DMA_SG_NO_LIST. Starting the device
+* requires a list to be created, and this function requires the device to be
+* started.
+*
+******************************************************************************/
+XStatus
+XEmac_SgSend(XEmac * InstancePtr, XBufDescriptor * BdPtr, int Delay)
+{
+	XStatus Result;
+	u32 BdControl;
+
+	XASSERT_NONVOID(InstancePtr != NULL);
+	XASSERT_NONVOID(BdPtr != NULL);
+	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	/*
+	 * Be sure the device is configured for scatter-gather DMA, then be sure
+	 * it is started.
+	 */
+	if (!XEmac_mIsSgDma(InstancePtr)) {
+		return XST_NOT_SGDMA;
+	}
+
+	/*
+	 * Set some descriptor control word defaults (source address increment
+	 * and local destination address) and the destination address
+	 * (the FIFO).  These are the same for every transmit descriptor.
+	 */
+	BdControl = XBufDescriptor_GetControl(BdPtr);
+	XBufDescriptor_SetControl(BdPtr, BdControl | XEM_DFT_SEND_BD_MASK);
+
+	XBufDescriptor_SetDestAddress(BdPtr,
+				      InstancePtr->BaseAddress +
+				      XEM_PFIFO_TXDATA_OFFSET);
+
+	/*
+	 * Put the descriptor in the send list. The DMA component accesses data
+	 * here that can also be modified in interrupt context, so a critical
+	 * section is required.
+	 */
+	XIIF_V123B_GINTR_DISABLE(InstancePtr->BaseAddress);
+
+	Result = XDmaChannel_PutDescriptor(&InstancePtr->SendChannel, BdPtr);
+	if (Result != XST_SUCCESS) {
+		XIIF_V123B_GINTR_ENABLE(InstancePtr->BaseAddress);
+		return Result;
+	}
+
+	/*
+	 * If this is the last buffer in the frame, commit the inserts and start
+	 * the DMA engine if necessary
+	 */
+	if (XBufDescriptor_IsLastControl(BdPtr)) {
+		Result = XDmaChannel_CommitPuts(&InstancePtr->SendChannel);
+		if (Result != XST_SUCCESS) {
+			XIIF_V123B_GINTR_ENABLE(InstancePtr->BaseAddress);
+			return Result;
+		}
+
+		if (Delay == XEM_SGDMA_NODELAY) {
+			/*
+			 * Start the DMA channel. Ignore the return status since we know the
+			 * list exists and has at least one entry and we don't care if the
+			 * channel is already started.  The DMA component accesses data here
+			 * that can be modified at interrupt or task levels, so a critical
+			 * section is required.
+			 */
+			(void) XDmaChannel_SgStart(&InstancePtr->SendChannel);
+		}
+	}
+
+	XIIF_V123B_GINTR_ENABLE(InstancePtr->BaseAddress);
+
+	return XST_SUCCESS;
+}
+
+/*****************************************************************************/
+/**
+*
+* Add a descriptor, with an attached empty buffer, into the receive descriptor
+* list. The buffer attached to the descriptor must be word-aligned. This is
+* used by the upper layer software during initialization when first setting up
+* the receive descriptors, and also during reception of frames to replace
+* filled buffers with empty buffers. This function can be called when the
+* device is started or stopped. Note that it does start the scatter-gather DMA
+* engine.  Although this is not necessary during initialization, it is not a
+* problem during initialization because the MAC receiver is not yet started.
+*
+* The buffer attached to the descriptor must be word-aligned on both the front
+* end and the back end.
+*
+* Notification of received frames are done asynchronously through the receive
+* callback function.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param BdPtr is a pointer to the buffer descriptor that will be added to the
+*        descriptor list.
+*
+* @return
+*
+* - XST_SUCCESS if a descriptor was successfully returned to the driver
+* - XST_NOT_SGDMA if the device is not in scatter-gather DMA mode
+* - XST_DMA_SG_LIST_FULL if the receive descriptor list is full
+* - XST_DMA_SG_BD_LOCKED if the DMA channel cannot insert the descriptor into
+*   the list because a locked descriptor exists at the insert point.
+* - XST_DMA_SG_NOTHING_TO_COMMIT if even after inserting a descriptor into the
+*   list, the DMA channel believes there are no new descriptors to commit.
+*
+* @internal
+*
+* A status that should never be returned from this function, although
+* the code is set up to handle it, is XST_DMA_SG_NO_LIST. Starting the device
+* requires a list to be created, and this function requires the device to be
+* started.
+*
+******************************************************************************/
+XStatus
+XEmac_SgRecv(XEmac * InstancePtr, XBufDescriptor * BdPtr)
+{
+	XStatus Result;
+	u32 BdControl;
+
+	XASSERT_NONVOID(InstancePtr != NULL);
+	XASSERT_NONVOID(BdPtr != NULL);
+	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	/*
+	 * Be sure the device is configured for scatter-gather DMA
+	 */
+	if (!XEmac_mIsSgDma(InstancePtr)) {
+		return XST_NOT_SGDMA;
+	}
+
+	/*
+	 * Set some descriptor control word defaults (destination address increment
+	 * and local source address) and the source address (the FIFO). These are
+	 * the same for every receive descriptor.
+	 */
+	BdControl = XBufDescriptor_GetControl(BdPtr);
+	XBufDescriptor_SetControl(BdPtr, BdControl | XEM_DFT_RECV_BD_MASK);
+	XBufDescriptor_SetSrcAddress(BdPtr,
+				     InstancePtr->BaseAddress +
+				     XEM_PFIFO_RXDATA_OFFSET);
+
+	/*
+	 * Put the descriptor into the channel's descriptor list and commit.
+	 * Although this function is likely called within interrupt context, there
+	 * is the possibility that the upper layer software queues it to a task.
+	 * In this case, a critical section is needed here to protect shared data
+	 * in the DMA component.
+	 */
+	XIIF_V123B_GINTR_DISABLE(InstancePtr->BaseAddress);
+
+	Result = XDmaChannel_PutDescriptor(&InstancePtr->RecvChannel, BdPtr);
+	if (Result != XST_SUCCESS) {
+		XIIF_V123B_GINTR_ENABLE(InstancePtr->BaseAddress);
+		return Result;
+	}
+
+	Result = XDmaChannel_CommitPuts(&InstancePtr->RecvChannel);
+	if (Result != XST_SUCCESS) {
+		XIIF_V123B_GINTR_ENABLE(InstancePtr->BaseAddress);
+		return Result;
+	}
+
+	/*
+	 * Start the DMA channel. Ignore the return status since we know the list
+	 * exists and has at least one entry and we don't care if the channel is
+	 * already started. The DMA component accesses data here that can be
+	 * modified at interrupt or task levels, so a critical section is required.
+	 */
+	(void) XDmaChannel_SgStart(&InstancePtr->RecvChannel);
+
+	XIIF_V123B_GINTR_ENABLE(InstancePtr->BaseAddress);
+
+	return XST_SUCCESS;
+}
+
+/*****************************************************************************/
+/**
+*
+* The interrupt handler for the Ethernet driver when configured with scatter-
+* gather DMA.
+*
+* Get the interrupt status from the IpIf to determine the source of the
+* interrupt.  The source can be: MAC, Recv Packet FIFO, Send Packet FIFO, Recv
+* DMA channel, or Send DMA channel. The packet FIFOs only interrupt during
+* "deadlock" conditions.
+*
+* @param InstancePtr is a pointer to the XEmac instance that just interrupted.
+*
+* @return
+*
+* None.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+void
+XEmac_IntrHandlerDma(void *InstancePtr)
+{
+	u32 IntrStatus;
+	XEmac *EmacPtr = (XEmac *) InstancePtr;
+
+	EmacPtr->Stats.TotalIntrs++;
+
+	/*
+	 * Get the interrupt status from the IPIF. There is no clearing of
+	 * interrupts in the IPIF. Interrupts must be cleared at the source.
+	 */
+	IntrStatus = XIIF_V123B_READ_DIPR(EmacPtr->BaseAddress);
+
+	/*
+	 * See which type of interrupt is being requested, and service it
+	 */
+	if (IntrStatus & XEM_IPIF_RECV_DMA_MASK) {	/* Receive DMA interrupt */
+		EmacPtr->Stats.RecvInterrupts++;
+		HandleDmaRecvIntr(EmacPtr);
+	}
+
+	if (IntrStatus & XEM_IPIF_SEND_DMA_MASK) {	/* Send DMA interrupt */
+		EmacPtr->Stats.XmitInterrupts++;
+		HandleDmaSendIntr(EmacPtr);
+	}
+
+	if (IntrStatus & XEM_IPIF_EMAC_MASK) {	/* MAC interrupt */
+		EmacPtr->Stats.EmacInterrupts++;
+		HandleEmacDmaIntr(EmacPtr);
+	}
+
+	if (IntrStatus & XEM_IPIF_RECV_FIFO_MASK) {	/* Receive FIFO interrupt */
+		EmacPtr->Stats.RecvInterrupts++;
+		XEmac_CheckFifoRecvError(EmacPtr);
+	}
+
+	if (IntrStatus & XEM_IPIF_SEND_FIFO_MASK) {	/* Send FIFO interrupt */
+		EmacPtr->Stats.XmitInterrupts++;
+		XEmac_CheckFifoSendError(EmacPtr);
+	}
+
+	if (IntrStatus & XIIF_V123B_ERROR_MASK) {
+		/*
+		 * An error occurred internal to the IPIF. This is more of a debug and
+		 * integration issue rather than a production error. Don't do anything
+		 * other than clear it, which provides a spot for software to trap
+		 * on the interrupt and begin debugging.
+		 */
+		XIIF_V123B_WRITE_DISR(EmacPtr->BaseAddress,
+				      XIIF_V123B_ERROR_MASK);
+	}
+}
+
+/*****************************************************************************/
+/**
+*
+* Set the packet count threshold for this device. The device must be stopped
+* before setting the threshold. The packet count threshold is used for interrupt
+* coalescing, which reduces the frequency of interrupts from the device to the
+* processor. In this case, the scatter-gather DMA engine only interrupts when
+* the packet count threshold is reached, instead of interrupting for each packet.
+* A packet is a generic term used by the scatter-gather DMA engine, and is
+* equivalent to an Ethernet frame in our case.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param Direction indicates the channel, send or receive, from which the
+*        threshold register is read.
+* @param Threshold is the value of the packet threshold count used during
+*        interrupt coalescing. A value of 0 disables the use of packet threshold
+*        by the hardware.
+*
+* @return
+*
+* - XST_SUCCESS if the threshold was successfully set
+* - XST_NOT_SGDMA if the MAC is not configured for scatter-gather DMA
+* - XST_DEVICE_IS_STARTED if the device has not been stopped
+* - XST_INVALID_PARAM if the Direction parameter is invalid. Turning on
+*   asserts would also catch this error.
+*
+* @note
+*
+* The packet threshold could be set to larger than the number of descriptors
+* allocated to the DMA channel. In this case, the wait bound will take over
+* and always indicate data arrival. There was a check in this function that
+* returned an error if the treshold was larger than the number of descriptors,
+* but that was removed because users would then have to set the threshold
+* only after they set descriptor space, which is an order dependency that
+* caused confustion.
+*
+******************************************************************************/
+XStatus
+XEmac_SetPktThreshold(XEmac * InstancePtr, u32 Direction, u8 Threshold)
+{
+	XASSERT_NONVOID(InstancePtr != NULL);
+	XASSERT_NONVOID(Direction == XEM_SEND || Direction == XEM_RECV);
+	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	/*
+	 * Be sure device is configured for scatter-gather DMA and has been stopped
+	 */
+	if (!XEmac_mIsSgDma(InstancePtr)) {
+		return XST_NOT_SGDMA;
+	}
+
+	if (InstancePtr->IsStarted == XCOMPONENT_IS_STARTED) {
+		return XST_DEVICE_IS_STARTED;
+	}
+
+	/*
+	 * Based on the direction, set the packet threshold in the
+	 * corresponding DMA channel component.  Default to the receive
+	 * channel threshold register (if an invalid Direction is passed).
+	 */
+	switch (Direction) {
+	case XEM_SEND:
+		return XDmaChannel_SetPktThreshold(&InstancePtr->SendChannel,
+						   Threshold);
+
+	case XEM_RECV:
+		return XDmaChannel_SetPktThreshold(&InstancePtr->RecvChannel,
+						   Threshold);
+
+	default:
+		return XST_INVALID_PARAM;
+	}
+}
+
+/*****************************************************************************/
+/**
+*
+* Get the value of the packet count threshold for this driver/device. The packet
+* count threshold is used for interrupt coalescing, which reduces the frequency
+* of interrupts from the device to the processor. In this case, the
+* scatter-gather DMA engine only interrupts when the packet count threshold is
+* reached, instead of interrupting for each packet. A packet is a generic term
+* used by the scatter-gather DMA engine, and is equivalent to an Ethernet frame
+* in our case.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param Direction indicates the channel, send or receive, from which the
+*        threshold register is read.
+* @param ThreshPtr is a pointer to the byte into which the current value of the
+*        packet threshold register will be copied. An output parameter. A value
+*        of 0 indicates the use of packet threshold by the hardware is disabled.
+*
+* @return
+*
+* - XST_SUCCESS if the packet threshold was retrieved successfully
+* - XST_NOT_SGDMA if the MAC is not configured for scatter-gather DMA
+* - XST_INVALID_PARAM if the Direction parameter is invalid. Turning on
+*   asserts would also catch this error.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+XStatus
+XEmac_GetPktThreshold(XEmac * InstancePtr, u32 Direction, u8 * ThreshPtr)
+{
+	XASSERT_NONVOID(InstancePtr != NULL);
+	XASSERT_NONVOID(Direction == XEM_SEND || Direction == XEM_RECV);
+	XASSERT_NONVOID(ThreshPtr != NULL);
+	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	if (!XEmac_mIsSgDma(InstancePtr)) {
+		return XST_NOT_SGDMA;
+	}
+
+	/*
+	 * Based on the direction, return the packet threshold set in the
+	 * corresponding DMA channel component.  Default to the value in
+	 * the receive channel threshold register (if an invalid Direction
+	 * is passed).
+	 */
+	switch (Direction) {
+	case XEM_SEND:
+		*ThreshPtr =
+		    XDmaChannel_GetPktThreshold(&InstancePtr->SendChannel);
+		break;
+
+	case XEM_RECV:
+		*ThreshPtr =
+		    XDmaChannel_GetPktThreshold(&InstancePtr->RecvChannel);
+		break;
+
+	default:
+		return XST_INVALID_PARAM;
+	}
+
+	return XST_SUCCESS;
+}
+
+/*****************************************************************************/
+/**
+*
+* Set the packet wait bound timer for this driver/device. The device must be
+* stopped before setting the timer value. The packet wait bound is used during
+* interrupt coalescing to trigger an interrupt when not enough packets have been
+* received to reach the packet count threshold. A packet is a generic term used
+* by the scatter-gather DMA engine, and is equivalent to an Ethernet frame in
+* our case. The timer is in milliseconds.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param Direction indicates the channel, send or receive, from which the
+*        threshold register is read.
+* @param TimerValue is the value of the packet wait bound used during interrupt
+*        coalescing. It is in milliseconds in the range 0  - 1023. A value of 0
+*        disables the packet wait bound timer.
+*
+* @return
+*
+* - XST_SUCCESS if the packet wait bound was set successfully
+* - XST_NOT_SGDMA if the MAC is not configured for scatter-gather DMA
+* - XST_DEVICE_IS_STARTED if the device has not been stopped
+* - XST_INVALID_PARAM if the Direction parameter is invalid. Turning on
+*   asserts would also catch this error.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+XStatus
+XEmac_SetPktWaitBound(XEmac * InstancePtr, u32 Direction, u32 TimerValue)
+{
+	XASSERT_NONVOID(InstancePtr != NULL);
+	XASSERT_NONVOID(Direction == XEM_SEND || Direction == XEM_RECV);
+	XASSERT_NONVOID(TimerValue <= XEM_SGDMA_MAX_WAITBOUND);
+	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	/*
+	 * Be sure device is configured for scatter-gather DMA and has been stopped
+	 */
+	if (!XEmac_mIsSgDma(InstancePtr)) {
+		return XST_NOT_SGDMA;
+	}
+
+	if (InstancePtr->IsStarted == XCOMPONENT_IS_STARTED) {
+		return XST_DEVICE_IS_STARTED;
+	}
+
+	/*
+	 * Based on the direction, set the packet wait bound in the
+	 * corresponding DMA channel component.  Default to the receive
+	 * channel wait bound register (if an invalid Direction is passed).
+	 */
+	switch (Direction) {
+	case XEM_SEND:
+		XDmaChannel_SetPktWaitBound(&InstancePtr->SendChannel,
+					    TimerValue);
+		break;
+
+	case XEM_RECV:
+		XDmaChannel_SetPktWaitBound(&InstancePtr->RecvChannel,
+					    TimerValue);
+		break;
+
+	default:
+		return XST_INVALID_PARAM;
+	}
+
+	return XST_SUCCESS;
+}
+
+/*****************************************************************************/
+/**
+*
+* Get the packet wait bound timer for this driver/device. The packet wait bound
+* is used during interrupt coalescing to trigger an interrupt when not enough
+* packets have been received to reach the packet count threshold. A packet is a
+* generic term used by the scatter-gather DMA engine, and is equivalent to an
+* Ethernet frame in our case. The timer is in milliseconds.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param Direction indicates the channel, send or receive, from which the
+*        threshold register is read.
+* @param WaitPtr is a pointer to the byte into which the current value of the
+*        packet wait bound register will be copied. An output parameter. Units
+*        are in milliseconds in the range 0  - 1023. A value of 0 indicates the
+*        packet wait bound timer is disabled.
+*
+* @return
+*
+* - XST_SUCCESS if the packet wait bound was retrieved successfully
+* - XST_NOT_SGDMA if the MAC is not configured for scatter-gather DMA
+* - XST_INVALID_PARAM if the Direction parameter is invalid. Turning on
+*   asserts would also catch this error.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+XStatus
+XEmac_GetPktWaitBound(XEmac * InstancePtr, u32 Direction, u32 * WaitPtr)
+{
+	XASSERT_NONVOID(InstancePtr != NULL);
+	XASSERT_NONVOID(Direction == XEM_SEND || Direction == XEM_RECV);
+	XASSERT_NONVOID(WaitPtr != NULL);
+	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	if (!XEmac_mIsSgDma(InstancePtr)) {
+		return XST_NOT_SGDMA;
+	}
+
+	/*
+	 * Based on the direction, return the packet wait bound set in the
+	 * corresponding DMA channel component.  Default to the value in
+	 * the receive channel wait bound register (if an invalid Direction
+	 * is passed).
+	 */
+	switch (Direction) {
+	case XEM_SEND:
+		*WaitPtr =
+		    XDmaChannel_GetPktWaitBound(&InstancePtr->SendChannel);
+		break;
+
+	case XEM_RECV:
+		*WaitPtr =
+		    XDmaChannel_GetPktWaitBound(&InstancePtr->RecvChannel);
+		break;
+
+	default:
+		return XST_INVALID_PARAM;
+	}
+
+	return XST_SUCCESS;
+}
+
+/*****************************************************************************/
+/**
+*
+* Give the driver the memory space to be used for the scatter-gather DMA
+* receive descriptor list. This function should only be called once, during
+* initialization of the Ethernet driver. The memory space must be big enough
+* to hold some number of descriptors, depending on the needs of the system.
+* The xemac.h file defines minimum and default numbers of descriptors
+* which can be used to allocate this memory space.
+*
+* The memory space must be word-aligned. An assert will occur if asserts are
+* turned on and the memory is not word-aligned.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param MemoryPtr is a pointer to the word-aligned memory.
+* @param ByteCount is the length, in bytes, of the memory space.
+*
+* @return
+*
+* - XST_SUCCESS if the space was initialized successfully
+* - XST_NOT_SGDMA if the MAC is not configured for scatter-gather DMA
+* - XST_DMA_SG_LIST_EXISTS if this list space has already been created
+*
+* @note
+*
+* If the device is configured for scatter-gather DMA, this function must be
+* called AFTER the XEmac_Initialize() function because the DMA channel
+* components must be initialized before the memory space is set.
+*
+******************************************************************************/
+XStatus
+XEmac_SetSgRecvSpace(XEmac * InstancePtr, u32 * MemoryPtr, u32 ByteCount)
+{
+	XASSERT_NONVOID(InstancePtr != NULL);
+	XASSERT_NONVOID(MemoryPtr != NULL);
+	XASSERT_NONVOID(ByteCount != 0);
+	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	if (!XEmac_mIsSgDma(InstancePtr)) {
+		return XST_NOT_SGDMA;
+	}
+
+	return XDmaChannel_CreateSgList(&InstancePtr->RecvChannel, MemoryPtr,
+					ByteCount);
+}
+
+/*****************************************************************************/
+/**
+*
+* Give the driver the memory space to be used for the scatter-gather DMA
+* transmit descriptor list. This function should only be called once, during
+* initialization of the Ethernet driver. The memory space must be big enough
+* to hold some number of descriptors, depending on the needs of the system.
+* The xemac.h file defines minimum and default numbers of descriptors
+* which can be used to allocate this memory space.
+*
+* The memory space must be word-aligned. An assert will occur if asserts are
+* turned on and the memory is not word-aligned.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param MemoryPtr is a pointer to the word-aligned memory.
+* @param ByteCount is the length, in bytes, of the memory space.
+*
+* @return
+*
+* - XST_SUCCESS if the space was initialized successfully
+* - XST_NOT_SGDMA if the MAC is not configured for scatter-gather DMA
+* - XST_DMA_SG_LIST_EXISTS if this list space has already been created
+*
+* @note
+*
+* If the device is configured for scatter-gather DMA, this function must be
+* called AFTER the XEmac_Initialize() function because the DMA channel
+* components must be initialized before the memory space is set.
+*
+******************************************************************************/
+XStatus
+XEmac_SetSgSendSpace(XEmac * InstancePtr, u32 * MemoryPtr, u32 ByteCount)
+{
+	XASSERT_NONVOID(InstancePtr != NULL);
+	XASSERT_NONVOID(MemoryPtr != NULL);
+	XASSERT_NONVOID(ByteCount != 0);
+	XASSERT_NONVOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	if (!XEmac_mIsSgDma(InstancePtr)) {
+		return XST_NOT_SGDMA;
+	}
+
+	return XDmaChannel_CreateSgList(&InstancePtr->SendChannel, MemoryPtr,
+					ByteCount);
+}
+
+/*****************************************************************************/
+/**
+*
+* Set the callback function for handling received frames in scatter-gather DMA
+* mode.  The upper layer software should call this function during
+* initialization.  The callback is called once per frame received. The head of
+* a descriptor list is passed in along with the number of descriptors in the
+* list. Before leaving the callback, the upper layer software should attach a
+* new buffer to each descriptor in the list.
+*
+* The callback is invoked by the driver within interrupt context, so it needs
+* to do its job quickly. Sending the received frame up the protocol stack
+* should be done at task-level. If there are other potentially slow operations
+* within the callback, these too should be done at task-level.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param CallBackRef is a reference pointer to be passed back to the adapter in
+*        the callback. This helps the adapter correlate the callback to a
+*        particular driver.
+* @param FuncPtr is the pointer to the callback function.
+*
+* @return
+*
+* None.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+void
+XEmac_SetSgRecvHandler(XEmac * InstancePtr, void *CallBackRef,
+		       XEmac_SgHandler FuncPtr)
+{
+	/*
+	 * Asserted IsDmaSg here instead of run-time check because there is really
+	 * no ill-effects of setting these when not configured for scatter-gather.
+	 */
+	XASSERT_VOID(InstancePtr != NULL);
+	XASSERT_VOID(FuncPtr != NULL);
+	XASSERT_VOID(XEmac_mIsSgDma(InstancePtr));
+	XASSERT_VOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	InstancePtr->SgRecvHandler = FuncPtr;
+	InstancePtr->SgRecvRef = CallBackRef;
+}
+
+/*****************************************************************************/
+/**
+*
+* Set the callback function for handling confirmation of transmitted frames in
+* scatter-gather DMA mode.  The upper layer software should call this function
+* during initialization.  The callback is called once per frame sent. The head
+* of a descriptor list is passed in along with the number of descriptors in
+* the list. The callback is responsible for freeing buffers attached to these
+* descriptors.
+*
+* The callback is invoked by the driver within interrupt context, so it needs
+* to do its job quickly. If there are potentially slow operations within the
+* callback, these should be done at task-level.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+* @param CallBackRef is a reference pointer to be passed back to the adapter in
+*        the callback. This helps the adapter correlate the callback to a
+*        particular driver.
+* @param FuncPtr is the pointer to the callback function.
+*
+* @return
+*
+* None.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+void
+XEmac_SetSgSendHandler(XEmac * InstancePtr, void *CallBackRef,
+		       XEmac_SgHandler FuncPtr)
+{
+	/*
+	 * Asserted IsDmaSg here instead of run-time check because there is really
+	 * no ill-effects of setting these when not configured for scatter-gather.
+	 */
+	XASSERT_VOID(InstancePtr != NULL);
+	XASSERT_VOID(FuncPtr != NULL);
+	XASSERT_VOID(XEmac_mIsSgDma(InstancePtr));
+	XASSERT_VOID(InstancePtr->IsReady == XCOMPONENT_IS_READY);
+
+	InstancePtr->SgSendHandler = FuncPtr;
+	InstancePtr->SgSendRef = CallBackRef;
+}
+
+/*****************************************************************************/
+/*
+*
+* Handle an interrupt from the DMA receive channel. DMA interrupts are:
+*
+* - DMA error. DMA encountered a bus error or timeout. This is a fatal error
+*   that requires reset of the channel.  The driver calls the error handler
+*   of the upper layer software with an error code indicating the device should
+*   be reset.
+* - Packet count threshold reached.  For scatter-gather operations, indicates
+*   the threshold for the number of packets not serviced by software has been
+*   reached. The driver behaves as follows:
+*       - Get the value of the packet counter, which tells us how many packets
+*         are ready to be serviced
+*       - For each packet
+*           - For each descriptor, remove it from the scatter-gather list
+*           - Check for the last descriptor in the frame, and if set
+*               - Bump frame statistics
+*               - Call the scatter-gather receive callback function
+*               - Decrement the packet counter by one
+*       Note that there are no receive errors reported in the status word of
+*       the buffer descriptor.  If receive errors occur, the MAC drops the
+*       packet, and we only find out about the errors through various error
+*       count registers.
+* - Packet wait bound reached.  For scatter-gather, indicates the time to wait
+*   for the next packet has expired.  The driver follows the same logic as when
+*   the packet count threshold interrupt is received.
+* - Scatter-gather end acknowledge.  Hardware has reached the end of the
+*   descriptor list.  The driver follows the same logic as when the packet count
+*   threshold interrupt is received. In addition, the driver restarts the DMA
+*   scatter-gather channel in case there are newly inserted descriptors.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+*
+* @return
+*
+* Although the function returns void, there are asynchronous errors that can
+* be generated (by calling the ErrorHandler) from this function.  These are:
+* - XST_DMA_SG_LIST_EMPTY indicates we tried to get a buffer descriptor from the
+*   DMA channel, but there was not one ready for software.
+* - XST_DMA_ERROR indicates a DMA bus error or timeout occurred. This is a fatal
+*   error that requires reset.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+static void
+HandleDmaRecvIntr(XEmac * InstancePtr)
+{
+	u32 IntrStatus;
+
+	/*
+	 * Read the interrupt status
+	 */
+	IntrStatus = XDmaChannel_GetIntrStatus(&InstancePtr->RecvChannel);
+
+	/*
+	 * For packet threshold or wait bound interrupts, process desciptors. Also
+	 * process descriptors on a SG end acknowledgement, which means the end of
+	 * the descriptor list has been reached by the hardware. For receive, this
+	 * is potentially trouble since it means the descriptor list is full,
+	 * unless software can process enough packets quickly enough so the
+	 * hardware has room to put new packets.
+	 */
+	if (IntrStatus & (XDC_IXR_PKT_THRESHOLD_MASK |
+			  XDC_IXR_PKT_WAIT_BOUND_MASK | XDC_IXR_SG_END_MASK)) {
+		XStatus Result = XST_SUCCESS;
+		u32 NumFrames;
+		u32 NumProcessed;
+		u32 NumBuffers;
+		u32 NumBytes;
+		u32 IsLast;
+		XBufDescriptor *FirstBdPtr;
+		XBufDescriptor *BdPtr;
+
+		/*
+		 * Get the number of unserviced packets
+		 */
+		NumFrames = XDmaChannel_GetPktCount(&InstancePtr->RecvChannel);
+
+		for (NumProcessed = 0; NumProcessed < NumFrames; NumProcessed++) {
+			IsLast = FALSE;
+			FirstBdPtr = NULL;
+			NumBuffers = 0;
+			NumBytes = 0;
+
+			/*
+			 * For each packet, get the descriptor from the list. On the
+			 * last one in the frame, make the callback to the upper layer.
+			 */
+			while (!IsLast) {
+				Result =
+				    XDmaChannel_GetDescriptor(&InstancePtr->
+							      RecvChannel,
+							      &BdPtr);
+				if (Result != XST_SUCCESS) {
+					/*
+					 * An error getting a buffer descriptor from the list.
+					 * This should not happen, but if it does, report it to
+					 * the error callback and break out of the loops to service
+					 * other interrupts.
+					 */
+					InstancePtr->ErrorHandler(InstancePtr->
+								  ErrorRef,
+								  Result);
+					break;
+				}
+
+				/*
+				 * Keep a pointer to the first descriptor in the list, as it
+				 * will be passed to the upper layers in a bit. By the fact
+				 * that we received this packet means no errors occurred, so
+				 * no need to check the device status word for errors.
+				 */
+				if (FirstBdPtr == NULL) {
+					FirstBdPtr = BdPtr;
+				}
+
+				NumBytes += XBufDescriptor_GetLength(BdPtr);
+
+				/*
+				 * Check to see if this is the last descriptor in the frame,
+				 * and if so, set the IsLast flag to get out of the loop.
+				 */
+				if (XBufDescriptor_IsLastStatus(BdPtr)) {
+					IsLast = TRUE;
+				}
+
+				/*
+				 * Bump the number of buffers in this packet
+				 */
+				NumBuffers++;
+
+			}	/* end while loop */
+
+			/*
+			 * Check for error that occurred inside the while loop, and break
+			 * out of the for loop if there was one so other interrupts can
+			 * be serviced.
+			 */
+			if (Result != XST_SUCCESS) {
+				break;
+			}
+
+			InstancePtr->Stats.RecvFrames++;
+			InstancePtr->Stats.RecvBytes += NumBytes;
+
+			/*
+			 * Make the callback to the upper layers, passing it the first
+			 * descriptor in the packet and the number of descriptors in the
+			 * packet.
+			 */
+			InstancePtr->SgRecvHandler(InstancePtr->SgRecvRef,
+						   FirstBdPtr, NumBuffers);
+
+			/*
+			 * Decrement the packet count register to reflect the fact we
+			 * just processed a packet
+			 */
+			XDmaChannel_DecrementPktCount(&InstancePtr->
+						      RecvChannel);
+
+		}		/* end for loop */
+
+		/*
+		 * If the interrupt was an end-ack, check the descriptor list again to
+		 * see if it is empty. If not, go ahead and restart the scatter-gather
+		 * channel. This is to fix a possible race condition where, on receive,
+		 * the driver attempted to start a scatter-gather channel that was
+		 * already started, which resulted in no action from the XDmaChannel
+		 * component. But, just after the XDmaChannel component saw that the
+		 * hardware was already started, the hardware stopped because it
+		 * reached the end of the list.  In that case, this interrupt is
+		 * generated and we can restart the hardware here.
+		 */
+		if (IntrStatus & XDC_IXR_SG_END_MASK) {
+			/*
+			 * Ignore the return status since we know the list exists and we
+			 * don't care if the list is empty or the channel is already started.
+			 */
+			(void) XDmaChannel_SgStart(&InstancePtr->RecvChannel);
+		}
+	}
+
+	/*
+	 * All interrupts are handled (except the error below) so acknowledge
+	 * (clear) the interrupts by writing the value read above back to the status
+	 * register. The packet count interrupt must be acknowledged after the
+	 * decrement, otherwise it will come right back. We clear the interrupts
+	 * before we handle the error interrupt because the ErrorHandler should
+	 * result in a reset, which clears the interrupt status register. So we
+	 * don't want to toggle the interrupt back on by writing the interrupt
+	 * status register with an old value after a reset.
+	 */
+	XDmaChannel_SetIntrStatus(&InstancePtr->RecvChannel, IntrStatus);
+
+	/*
+	 * Check for DMA errors and call the error callback function if an error
+	 * occurred (DMA bus or timeout error), which should result in a reset of
+	 * the device by the upper layer software.
+	 */
+	if (IntrStatus & XDC_IXR_DMA_ERROR_MASK) {
+		InstancePtr->Stats.DmaErrors++;
+		InstancePtr->ErrorHandler(InstancePtr->ErrorRef, XST_DMA_ERROR);
+	}
+}
+
+/*****************************************************************************/
+/*
+*
+* Handle an interrupt from the DMA send channel. DMA interrupts are:
+*
+* - DMA error. DMA encountered a bus error or timeout. This is a fatal error
+*   that requires reset of the channel.  The driver calls the error handler
+*   of the upper layer software with an error code indicating the device should
+*   be reset.
+* - Packet count threshold reached.  For scatter-gather operations, indicates
+*   the threshold for the number of packets not serviced by software has been
+*   reached. The driver behaves as follows:
+*       - Get the value of the packet counter, which tells us how many packets
+*         are ready to be serviced
+*       - For each packet
+*           - For each descriptor, remove it from the scatter-gather list
+*           - Check for the last descriptor in the frame, and if set
+*               - Bump frame statistics
+*               - Call the scatter-gather receive callback function
+*               - Decrement the packet counter by one
+*       Note that there are no receive errors reported in the status word of
+*       the buffer descriptor.  If receive errors occur, the MAC drops the
+*       packet, and we only find out about the errors through various error
+*       count registers.
+* - Packet wait bound reached.  For scatter-gather, indicates the time to wait
+*   for the next packet has expired.  The driver follows the same logic as when
+*   the packet count threshold interrupt is received.
+* - Scatter-gather end acknowledge.  Hardware has reached the end of the
+*   descriptor list.  The driver follows the same logic as when the packet count
+*   threshold interrupt is received. In addition, the driver restarts the DMA
+*   scatter-gather channel in case there are newly inserted descriptors.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+*
+* @return
+*
+* Although the function returns void, there are asynchronous errors
+* that can be generated from this function.  These are:
+* - XST_DMA_SG_LIST_EMPTY indicates we tried to get a buffer descriptor from
+*   the DMA channel, but there was not one ready for software.
+* - XST_DMA_ERROR indicates a DMA bus error or timeout occurred. This is a
+*   fatal error that requires reset.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+static void
+HandleDmaSendIntr(XEmac * InstancePtr)
+{
+	u32 IntrStatus;
+
+	/*
+	 * Read the interrupt status
+	 */
+	IntrStatus = XDmaChannel_GetIntrStatus(&InstancePtr->SendChannel);
+
+	/*
+	 * For packet threshold or wait bound interrupt, process descriptors. Also
+	 * process descriptors on a SG end acknowledgement, which means the end of
+	 * the descriptor list has been reached by the hardware. For transmit,
+	 * this is a normal condition during times of light traffic.  In fact, the
+	 * wait bound interrupt may be masked for transmit since the end-ack would
+	 * always occur before the wait bound expires.
+	 */
+	if (IntrStatus & (XDC_IXR_PKT_THRESHOLD_MASK |
+			  XDC_IXR_PKT_WAIT_BOUND_MASK | XDC_IXR_SG_END_MASK)) {
+		XStatus Result = XST_SUCCESS;
+		u32 NumFrames;
+		u32 NumProcessed;
+		u32 NumBuffers;
+		u32 NumBytes;
+		u32 IsLast;
+		XBufDescriptor *FirstBdPtr;
+		XBufDescriptor *BdPtr;
+
+		/*
+		 * Get the number of unserviced packets
+		 */
+		NumFrames = XDmaChannel_GetPktCount(&InstancePtr->SendChannel);
+
+		for (NumProcessed = 0; NumProcessed < NumFrames; NumProcessed++) {
+			IsLast = FALSE;
+			FirstBdPtr = NULL;
+			NumBuffers = 0;
+			NumBytes = 0;
+
+			/*
+			 * For each frame, traverse the descriptor list and look for
+			 * errors. On the last one in the frame, make the callback.
+			 */
+			while (!IsLast) {
+				Result =
+				    XDmaChannel_GetDescriptor(&InstancePtr->
+							      SendChannel,
+							      &BdPtr);
+				if (Result != XST_SUCCESS) {
+					/*
+					 * An error getting a buffer descriptor from the list.
+					 * This should not happen, but if it does, report it to
+					 * the error callback and break out of the loops to service
+					 * other interrupts
+					 */
+					InstancePtr->ErrorHandler(InstancePtr->
+								  ErrorRef,
+								  Result);
+					break;
+				}
+
+				/*
+				 * Keep a pointer to the first descriptor in the list and
+				 * check the device status for errors. The device status is
+				 * only available in the first descriptor of a packet.
+				 */
+				if (FirstBdPtr == NULL) {
+					u32 XmitStatus;
+
+					FirstBdPtr = BdPtr;
+
+					XmitStatus =
+					    XBufDescriptor_GetDeviceStatus
+					    (BdPtr);
+					if (XmitStatus &
+					    XEM_TSR_EXCESS_DEFERRAL_MASK) {
+						InstancePtr->Stats.
+						    XmitExcessDeferral++;
+					}
+
+					if (XmitStatus &
+					    XEM_TSR_LATE_COLLISION_MASK) {
+						InstancePtr->Stats.
+						    XmitLateCollisionErrors++;
+					}
+				}
+
+				NumBytes += XBufDescriptor_GetLength(BdPtr);
+
+				/*
+				 * Check to see if this is the last descriptor in the frame,
+				 * and if so, set the IsLast flag to get out of the loop. The
+				 * transmit channel must check the last bit in the control
+				 * word, not the status word (the DMA engine does not update
+				 * the last bit in the status word for the transmit direction).
+				 */
+				if (XBufDescriptor_IsLastControl(BdPtr)) {
+					IsLast = TRUE;
+				}
+
+				/*
+				 * Bump the number of buffers in this packet
+				 */
+				NumBuffers++;
+
+			}	/* end while loop */
+
+			/*
+			 * Check for error that occurred inside the while loop, and break
+			 * out of the for loop if there was one so other interrupts can
+			 * be serviced.
+			 */
+			if (Result != XST_SUCCESS) {
+				break;
+			}
+
+			InstancePtr->Stats.XmitFrames++;
+			InstancePtr->Stats.XmitBytes += NumBytes;
+
+			/*
+			 * Make the callback to the upper layers, passing it the first
+			 * descriptor in the packet and the number of descriptors in the
+			 * packet.
+			 */
+			InstancePtr->SgSendHandler(InstancePtr->SgSendRef,
+						   FirstBdPtr, NumBuffers);
+
+			/*
+			 * Decrement the packet count register to reflect the fact we
+			 * just processed a packet
+			 */
+			XDmaChannel_DecrementPktCount(&InstancePtr->
+						      SendChannel);
+
+		}		/* end for loop */
+
+		/*
+		 * If the interrupt was an end-ack, check the descriptor list again to
+		 * see if it is empty. If not, go ahead and restart the scatter-gather
+		 * channel. This is to fix a possible race condition where, on transmit,
+		 * the driver attempted to start a scatter-gather channel that was
+		 * already started, which resulted in no action from the XDmaChannel
+		 * component. But, just after the XDmaChannel component saw that the
+		 * hardware was already started, the hardware stopped because it
+		 * reached the end of the list.  In that case, this interrupt is
+		 * generated and we can restart the hardware here.
+		 */
+		if (IntrStatus & XDC_IXR_SG_END_MASK) {
+			/*
+			 * Ignore the return status since we know the list exists and we
+			 * don't care if the list is empty or the channel is already started.
+			 */
+			(void) XDmaChannel_SgStart(&InstancePtr->SendChannel);
+		}
+	}
+
+	/*
+	 * All interrupts are handled (except the error below) so acknowledge
+	 * (clear) the interrupts by writing the value read above back to the status
+	 * register. The packet count interrupt must be acknowledged after the
+	 * decrement, otherwise it will come right back. We clear the interrupts
+	 * before we handle the error interrupt because the ErrorHandler should
+	 * result in a reset, which clears the interrupt status register. So we
+	 * don't want to toggle the interrupt back on by writing the interrupt
+	 * status register with an old value after a reset.
+	 */
+	XDmaChannel_SetIntrStatus(&InstancePtr->SendChannel, IntrStatus);
+
+	/*
+	 * Check for DMA errors and call the error callback function if an error
+	 * occurred (DMA bus or timeout error), which should result in a reset of
+	 * the device by the upper layer software.
+	 */
+	if (IntrStatus & XDC_IXR_DMA_ERROR_MASK) {
+		InstancePtr->Stats.DmaErrors++;
+		InstancePtr->ErrorHandler(InstancePtr->ErrorRef, XST_DMA_ERROR);
+	}
+}
+
+/*****************************************************************************/
+/*
+*
+* Handle an interrupt from the Ethernet MAC when configured with scatter-gather
+* DMA. The only interrupts handled in this case are errors.
+*
+* @param InstancePtr is a pointer to the XEmac instance to be worked on.
+*
+* @return
+*
+* None.
+*
+* @note
+*
+* None.
+*
+******************************************************************************/
+static void
+HandleEmacDmaIntr(XEmac * InstancePtr)
+{
+	u32 IntrStatus;
+
+	/*
+	 * When configured with DMA, the EMAC generates interrupts only when errors
+	 * occur. We clear the interrupts immediately so that any latched status
+	 * interrupt bits will reflect the true status of the device, and so any
+	 * pulsed interrupts (non-status) generated during the Isr will not be lost.
+	 */
+	IntrStatus = XIIF_V123B_READ_IISR(InstancePtr->BaseAddress);
+	XIIF_V123B_WRITE_IISR(InstancePtr->BaseAddress, IntrStatus);
+
+	/*
+	 * Check the MAC for errors
+	 */
+	XEmac_CheckEmacError(InstancePtr, IntrStatus);
+}