コード例 #1
0
int dma_free_channel(DMA_Handle_t handle	/*             */
    ) {
	int rc = 0;
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;

	if (down_interruptible(&gDMA.lock) < 0) {
		return -ERESTARTSYS;
	}

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		rc = -EINVAL;
		goto out;
	}

	devAttr = &DMA_gDeviceAttribute[channel->devType];

	if ((channel->flags & DMA_CHANNEL_FLAG_IS_DEDICATED) == 0) {
		channel->lastDevType = channel->devType;
		channel->devType = DMA_DEVICE_NONE;
	}
	channel->flags &= ~DMA_CHANNEL_FLAG_IN_USE;
	devAttr->flags &= ~DMA_DEVICE_FLAG_IN_USE;

out:
	up(&gDMA.lock);

	wake_up_interruptible(&gDMA.freeChannelQ);

	return rc;
}
コード例 #2
0
static int ConfigChannel(DMA_Handle_t handle)
{
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;
	int controllerIdx;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}
	devAttr = &DMA_gDeviceAttribute[channel->devType];
	controllerIdx = CONTROLLER_FROM_HANDLE(handle);

	if ((devAttr->flags & DMA_DEVICE_FLAG_PORT_PER_DMAC) != 0) {
		if (devAttr->config.transferType ==
		    dmacHw_TRANSFER_TYPE_MEM_TO_PERIPHERAL) {
			devAttr->config.dstPeripheralPort =
			    devAttr->dmacPort[controllerIdx];
		} else if (devAttr->config.transferType ==
			   dmacHw_TRANSFER_TYPE_PERIPHERAL_TO_MEM) {
			devAttr->config.srcPeripheralPort =
			    devAttr->dmacPort[controllerIdx];
		}
	}

	if (dmacHw_configChannel(channel->dmacHwHandle, &devAttr->config) != 0) {
		printk(KERN_ERR "ConfigChannel: dmacHw_configChannel failed\n");
		return -EIO;
	}

	return 0;
}
コード例 #3
0
int dma_stop_transfer(DMA_Handle_t handle)
{
	DMA_Channel_t *channel;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}

	dmacHw_stopTransfer(channel->dmacHwHandle);

	return 0;
}
コード例 #4
0
int dma_transfer(DMA_Handle_t handle,	/*            */
		 dmacHw_TRANSFER_TYPE_e transferType,	/*                                  */
		 dma_addr_t srcData,	/*                                      */
		 dma_addr_t dstData,	/*                                */
		 size_t numBytes	/*                                           */
    ) {
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;
	int rc = 0;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}

	devAttr = &DMA_gDeviceAttribute[channel->devType];

	if (devAttr->config.transferType != transferType) {
		return -EINVAL;
	}

	/*                                                                      */
	/*                                                                               */
	/*                                                         */

	{
		rc =
		     dma_alloc_descriptors(handle, transferType, srcData,
					   dstData, numBytes);
		if (rc != 0) {
			return rc;
		}
	}

	/*                           */

	devAttr->numBytes = numBytes;
	devAttr->transferStartTime = timer_get_tick_count();

	dmacHw_initiateTransfer(channel->dmacHwHandle, &devAttr->config,
				devAttr->ring.virtAddr);

	/*                                                     */

	return 0;
}
コード例 #5
0
ファイル: dma.c プロジェクト: Blueprint-Marketing/GCG-3.3
int dma_transfer(DMA_Handle_t handle,	/* DMA Handle */
		 dmacHw_TRANSFER_TYPE_e transferType,	/* Type of transfer being performed */
		 dma_addr_t srcData,	/* Place to get data to write to device */
		 dma_addr_t dstData,	/* Pointer to device data address */
		 size_t numBytes	/* Number of bytes to transfer to the device */
    ) {
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;
	int rc = 0;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}

	devAttr = &DMA_gDeviceAttribute[channel->devType];

	if (devAttr->config.transferType != transferType) {
		return -EINVAL;
	}

	/* We keep track of the information about the previous request for this */
	/* device, and if the attributes match, then we can use the descriptors we setup */
	/* the last time, and not have to reinitialize everything. */

	{
		rc =
		     dma_alloc_descriptors(handle, transferType, srcData,
					   dstData, numBytes);
		if (rc != 0) {
			return rc;
		}
	}

	/* And kick off the transfer */

	devAttr->numBytes = numBytes;
	devAttr->transferStartTime = timer_get_tick_count();

	dmacHw_initiateTransfer(channel->dmacHwHandle, &devAttr->config,
				devAttr->ring.virtAddr);

	/* Since we got this far, everything went successfully */

	return 0;
}
コード例 #6
0
int dma_start_transfer(DMA_Handle_t handle)
{
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}
	devAttr = &DMA_gDeviceAttribute[channel->devType];

	dmacHw_initiateTransfer(channel->dmacHwHandle, &devAttr->config,
				devAttr->ring.virtAddr);

	/*                                                     */

	return 0;
}
コード例 #7
0
int dma_wait_transfer_done(DMA_Handle_t handle)
{
	DMA_Channel_t *channel;
	dmacHw_TRANSFER_STATUS_e status;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}

	while ((status =
		dmacHw_transferCompleted(channel->dmacHwHandle)) ==
	       dmacHw_TRANSFER_STATUS_BUSY) {
		;
	}

	if (status == dmacHw_TRANSFER_STATUS_ERROR) {
		printk(KERN_ERR "%s: DMA transfer failed\n", __func__);
		return -EIO;
	}
	return 0;
}
コード例 #8
0
int dma_init(void)
{
	int rc = 0;
	int controllerIdx;
	int channelIdx;
	DMA_Device_t devIdx;
	DMA_Channel_t *channel;
	DMA_Handle_t dedicatedHandle;

	memset(&gDMA, 0, sizeof(gDMA));

	sema_init(&gDMA.lock, 0);
	init_waitqueue_head(&gDMA.freeChannelQ);

	/*                         */

	dmacHw_initDma();

	/*                                                         */

	for (controllerIdx = 0; controllerIdx < DMA_NUM_CONTROLLERS;
	     controllerIdx++) {
		for (channelIdx = 0; channelIdx < DMA_NUM_CHANNELS;
		     channelIdx++) {
			channel =
			    &gDMA.controller[controllerIdx].channel[channelIdx];

			channel->flags = 0;
			channel->devType = DMA_DEVICE_NONE;
			channel->lastDevType = DMA_DEVICE_NONE;

#if (DMA_DEBUG_TRACK_RESERVATION)
			channel->fileName = "";
			channel->lineNum = 0;
#endif

			channel->dmacHwHandle =
			    dmacHw_getChannelHandle(dmacHw_MAKE_CHANNEL_ID
						    (controllerIdx,
						     channelIdx));
			dmacHw_initChannel(channel->dmacHwHandle);
		}
	}

	/*                                                      */

	gDMA.controller[0].channel[0].flags |= DMA_CHANNEL_FLAG_LARGE_FIFO;
	gDMA.controller[0].channel[1].flags |= DMA_CHANNEL_FLAG_LARGE_FIFO;
	gDMA.controller[1].channel[0].flags |= DMA_CHANNEL_FLAG_LARGE_FIFO;
	gDMA.controller[1].channel[1].flags |= DMA_CHANNEL_FLAG_LARGE_FIFO;

	/*                                                     */

	for (devIdx = 0; devIdx < DMA_NUM_DEVICE_ENTRIES; devIdx++) {
		DMA_DeviceAttribute_t *devAttr = &DMA_gDeviceAttribute[devIdx];

		if (((devAttr->flags & DMA_DEVICE_FLAG_NO_ISR) != 0)
		    && ((devAttr->flags & DMA_DEVICE_FLAG_IS_DEDICATED) == 0)) {
			printk(KERN_ERR
			       "DMA Device: %s Can only request NO_ISR for dedicated devices\n",
			       devAttr->name);
			rc = -EINVAL;
			goto out;
		}

		if ((devAttr->flags & DMA_DEVICE_FLAG_IS_DEDICATED) != 0) {
			/*                                                                 */

			if (devAttr->dedicatedController >= DMA_NUM_CONTROLLERS) {
				printk(KERN_ERR
				       "DMA Device: %s DMA Controller %d is out of range\n",
				       devAttr->name,
				       devAttr->dedicatedController);
				rc = -EINVAL;
				goto out;
			}

			if (devAttr->dedicatedChannel >= DMA_NUM_CHANNELS) {
				printk(KERN_ERR
				       "DMA Device: %s DMA Channel %d is out of range\n",
				       devAttr->name,
				       devAttr->dedicatedChannel);
				rc = -EINVAL;
				goto out;
			}

			dedicatedHandle =
			    MAKE_HANDLE(devAttr->dedicatedController,
					devAttr->dedicatedChannel);
			channel = HandleToChannel(dedicatedHandle);

			if ((channel->flags & DMA_CHANNEL_FLAG_IS_DEDICATED) !=
			    0) {
				printk
				    ("DMA Device: %s attempting to use same DMA Controller:Channel (%d:%d) as %s\n",
				     devAttr->name,
				     devAttr->dedicatedController,
				     devAttr->dedicatedChannel,
				     DMA_gDeviceAttribute[channel->devType].
				     name);
				rc = -EBUSY;
				goto out;
			}

			channel->flags |= DMA_CHANNEL_FLAG_IS_DEDICATED;
			channel->devType = devIdx;

			if (devAttr->flags & DMA_DEVICE_FLAG_NO_ISR) {
				channel->flags |= DMA_CHANNEL_FLAG_NO_ISR;
			}

			/*                                                                           */
			/*          */

			ConfigChannel(dedicatedHandle);
		}
	}

	/*                                                */

	for (controllerIdx = 0; controllerIdx < DMA_NUM_CONTROLLERS;
	     controllerIdx++) {
		for (channelIdx = 0; channelIdx < DMA_NUM_CHANNELS;
		     channelIdx++) {
			channel =
			    &gDMA.controller[controllerIdx].channel[channelIdx];

			if ((channel->flags & DMA_CHANNEL_FLAG_NO_ISR) == 0) {
				snprintf(channel->name, sizeof(channel->name),
					 "dma %d:%d %s", controllerIdx,
					 channelIdx,
					 channel->devType ==
					 DMA_DEVICE_NONE ? "" :
					 DMA_gDeviceAttribute[channel->devType].
					 name);

				rc =
				     request_irq(IRQ_DMA0C0 +
						 (controllerIdx *
						  DMA_NUM_CHANNELS) +
						 channelIdx,
						 dma_interrupt_handler,
						 IRQF_DISABLED, channel->name,
						 channel);
				if (rc != 0) {
					printk(KERN_ERR
					       "request_irq for IRQ_DMA%dC%d failed\n",
					       controllerIdx, channelIdx);
				}
			}
		}
	}

	/*                                                 */

	gDmaDir = proc_mkdir("dma", NULL);

	if (gDmaDir == NULL) {
		printk(KERN_ERR "Unable to create /proc/dma\n");
	} else {
		create_proc_read_entry("channels", 0, gDmaDir,
				       dma_proc_read_channels, NULL);
		create_proc_read_entry("devices", 0, gDmaDir,
				       dma_proc_read_devices, NULL);
	}

out:

	up(&gDMA.lock);

	return rc;
}
コード例 #9
0
int dma_alloc_double_dst_descriptors(DMA_Handle_t handle,	/*            */
				     dma_addr_t srcData,	/*                                 */
				     dma_addr_t dstData1,	/*                                              */
				     dma_addr_t dstData2,	/*                                               */
				     size_t numBytes	/*                                            */
    ) {
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;
	int numDst1Descriptors;
	int numDst2Descriptors;
	int numDescriptors;
	size_t ringBytesRequired;
	int rc = 0;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}

	devAttr = &DMA_gDeviceAttribute[channel->devType];

	/*                                          */

	/*                                                           */
	/*                                     */

	numDst1Descriptors =
	     dmacHw_calculateDescriptorCount(&devAttr->config, (void *)srcData,
					     (void *)dstData1, numBytes);
	if (numDst1Descriptors < 0) {
		return -EINVAL;
	}
	numDst2Descriptors =
	     dmacHw_calculateDescriptorCount(&devAttr->config, (void *)srcData,
					     (void *)dstData2, numBytes);
	if (numDst2Descriptors < 0) {
		return -EINVAL;
	}
	numDescriptors = numDst1Descriptors + numDst2Descriptors;
	/*                                                 */

	/*                                                                                      */
	/*            */

	ringBytesRequired = dmacHw_descriptorLen(numDescriptors);

	/*                                                       */

	if (ringBytesRequired > devAttr->ring.bytesAllocated) {
		/*                                                                      */
		/*                                                                         */
		/*                                             */

		might_sleep();

		/*                                                      */

		dma_free_descriptor_ring(&devAttr->ring);

		/*                         */

		rc =
		     dma_alloc_descriptor_ring(&devAttr->ring,
					       numDescriptors);
		if (rc < 0) {
			printk(KERN_ERR
			       "%s: dma_alloc_descriptor_ring(%d) failed\n",
			       __func__, ringBytesRequired);
			return rc;
		}
	}

	/*                                                                          */
	/*                                                                          */
	/*                                                            */

	if (dmacHw_initDescriptor(devAttr->ring.virtAddr,
				  devAttr->ring.physAddr,
				  devAttr->ring.bytesAllocated,
				  numDescriptors) < 0) {
		printk(KERN_ERR "%s: dmacHw_initDescriptor failed\n", __func__);
		return -EINVAL;
	}

	/*                                                                                 */
	/*                                                                   */

	if (dmacHw_setDataDescriptor(&devAttr->config,
				     devAttr->ring.virtAddr,
				     (void *)srcData,
				     (void *)dstData1, numBytes) < 0) {
		printk(KERN_ERR "%s: dmacHw_setDataDescriptor 1 failed\n",
		       __func__);
		return -EINVAL;
	}
	if (dmacHw_setDataDescriptor(&devAttr->config,
				     devAttr->ring.virtAddr,
				     (void *)srcData,
				     (void *)dstData2, numBytes) < 0) {
		printk(KERN_ERR "%s: dmacHw_setDataDescriptor 2 failed\n",
		       __func__);
		return -EINVAL;
	}

	/*                                                                            */
	/*                                         */

	devAttr->prevSrcData = 0;
	devAttr->prevDstData = 0;
	devAttr->prevNumBytes = 0;

	return numDescriptors;
}
コード例 #10
0
int dma_alloc_descriptors(DMA_Handle_t handle,	/*            */
			  dmacHw_TRANSFER_TYPE_e transferType,	/*                                  */
			  dma_addr_t srcData,	/*                                      */
			  dma_addr_t dstData,	/*                                */
			  size_t numBytes	/*                                           */
    ) {
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;
	int numDescriptors;
	size_t ringBytesRequired;
	int rc = 0;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}

	devAttr = &DMA_gDeviceAttribute[channel->devType];

	if (devAttr->config.transferType != transferType) {
		return -EINVAL;
	}

	/*                                          */

	/*                                                           */
	/*                                     */

	numDescriptors = dmacHw_calculateDescriptorCount(&devAttr->config,
							      (void *)srcData,
							      (void *)dstData,
							      numBytes);
	if (numDescriptors < 0) {
		printk(KERN_ERR "%s: dmacHw_calculateDescriptorCount failed\n",
		       __func__);
		return -EINVAL;
	}

	/*                                                                                      */
	/*            */

	ringBytesRequired = dmacHw_descriptorLen(numDescriptors);

	/*                                                       */

	if (ringBytesRequired > devAttr->ring.bytesAllocated) {
		/*                                                                      */
		/*                                                                         */
		/*                                             */

		might_sleep();

		/*                                                      */

		dma_free_descriptor_ring(&devAttr->ring);

		/*                         */

		rc =
		     dma_alloc_descriptor_ring(&devAttr->ring,
					       numDescriptors);
		if (rc < 0) {
			printk(KERN_ERR
			       "%s: dma_alloc_descriptor_ring(%d) failed\n",
			       __func__, numDescriptors);
			return rc;
		}
		/*                                        */

		if (dmacHw_initDescriptor(devAttr->ring.virtAddr,
					  devAttr->ring.physAddr,
					  devAttr->ring.bytesAllocated,
					  numDescriptors) < 0) {
			printk(KERN_ERR "%s: dmacHw_initDescriptor failed\n",
			       __func__);
			return -EINVAL;
		}
	} else {
		/*                                                                            */
		/*                                                                     */

		dmacHw_resetDescriptorControl(devAttr->ring.virtAddr);
	}

	/*                                                                                 */
	/*                                                                   */

	if (dmacHw_setDataDescriptor(&devAttr->config,
				     devAttr->ring.virtAddr,
				     (void *)srcData,
				     (void *)dstData, numBytes) < 0) {
		printk(KERN_ERR "%s: dmacHw_setDataDescriptor failed\n",
		       __func__);
		return -EINVAL;
	}

	/*                                                                              */
	/*                                                                             */

	devAttr->prevSrcData = srcData;
	devAttr->prevDstData = dstData;
	devAttr->prevNumBytes = numBytes;

	return 0;
}
コード例 #11
0
ファイル: dma.c プロジェクト: Blueprint-Marketing/GCG-3.3
int dma_alloc_double_dst_descriptors(DMA_Handle_t handle,	/* DMA Handle */
				     dma_addr_t srcData,	/* Physical address of source data */
				     dma_addr_t dstData1,	/* Physical address of first destination buffer */
				     dma_addr_t dstData2,	/* Physical address of second destination buffer */
				     size_t numBytes	/* Number of bytes in each destination buffer */
    ) {
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;
	int numDst1Descriptors;
	int numDst2Descriptors;
	int numDescriptors;
	size_t ringBytesRequired;
	int rc = 0;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}

	devAttr = &DMA_gDeviceAttribute[channel->devType];

	/* Figure out how many descriptors we need. */

	/* printk("srcData: 0x%08x dstData: 0x%08x, numBytes: %d\n", */
	/*        srcData, dstData, numBytes); */

	numDst1Descriptors =
	     dmacHw_calculateDescriptorCount(&devAttr->config, (void *)srcData,
					     (void *)dstData1, numBytes);
	if (numDst1Descriptors < 0) {
		return -EINVAL;
	}
	numDst2Descriptors =
	     dmacHw_calculateDescriptorCount(&devAttr->config, (void *)srcData,
					     (void *)dstData2, numBytes);
	if (numDst2Descriptors < 0) {
		return -EINVAL;
	}
	numDescriptors = numDst1Descriptors + numDst2Descriptors;
	/* printk("numDescriptors: %d\n", numDescriptors); */

	/* Check to see if we can reuse the existing descriptor ring, or if we need to allocate */
	/* a new one. */

	ringBytesRequired = dmacHw_descriptorLen(numDescriptors);

	/* printk("ringBytesRequired: %d\n", ringBytesRequired); */

	if (ringBytesRequired > devAttr->ring.bytesAllocated) {
		/* Make sure that this code path is never taken from interrupt context. */
		/* It's OK for an interrupt to initiate a DMA transfer, but the descriptor */
		/* allocation needs to have already been done. */

		might_sleep();

		/* Free the old descriptor ring and allocate a new one. */

		dma_free_descriptor_ring(&devAttr->ring);

		/* And allocate a new one. */

		rc =
		     dma_alloc_descriptor_ring(&devAttr->ring,
					       numDescriptors);
		if (rc < 0) {
			printk(KERN_ERR
			       "%s: dma_alloc_descriptor_ring(%d) failed\n",
			       __func__, ringBytesRequired);
			return rc;
		}
	}

	/* Setup the descriptor for this transfer. Since this function is used with */
	/* CONTINUOUS DMA operations, we need to reinitialize every time, otherwise */
	/* setDataDescriptor will keep trying to append onto the end. */

	if (dmacHw_initDescriptor(devAttr->ring.virtAddr,
				  devAttr->ring.physAddr,
				  devAttr->ring.bytesAllocated,
				  numDescriptors) < 0) {
		printk(KERN_ERR "%s: dmacHw_initDescriptor failed\n", __func__);
		return -EINVAL;
	}

	/* dma_alloc/free both set the prevSrc/DstData to 0. If they happen to be the same */
	/* as last time, then we don't need to call setDataDescriptor again. */

	if (dmacHw_setDataDescriptor(&devAttr->config,
				     devAttr->ring.virtAddr,
				     (void *)srcData,
				     (void *)dstData1, numBytes) < 0) {
		printk(KERN_ERR "%s: dmacHw_setDataDescriptor 1 failed\n",
		       __func__);
		return -EINVAL;
	}
	if (dmacHw_setDataDescriptor(&devAttr->config,
				     devAttr->ring.virtAddr,
				     (void *)srcData,
				     (void *)dstData2, numBytes) < 0) {
		printk(KERN_ERR "%s: dmacHw_setDataDescriptor 2 failed\n",
		       __func__);
		return -EINVAL;
	}

	/* You should use dma_start_transfer rather than dma_transfer_xxx so we don't */
	/* try to make the 'prev' variables right. */

	devAttr->prevSrcData = 0;
	devAttr->prevDstData = 0;
	devAttr->prevNumBytes = 0;

	return numDescriptors;
}
コード例 #12
0
ファイル: dma.c プロジェクト: Blueprint-Marketing/GCG-3.3
int dma_alloc_descriptors(DMA_Handle_t handle,	/* DMA Handle */
			  dmacHw_TRANSFER_TYPE_e transferType,	/* Type of transfer being performed */
			  dma_addr_t srcData,	/* Place to get data to write to device */
			  dma_addr_t dstData,	/* Pointer to device data address */
			  size_t numBytes	/* Number of bytes to transfer to the device */
    ) {
	DMA_Channel_t *channel;
	DMA_DeviceAttribute_t *devAttr;
	int numDescriptors;
	size_t ringBytesRequired;
	int rc = 0;

	channel = HandleToChannel(handle);
	if (channel == NULL) {
		return -ENODEV;
	}

	devAttr = &DMA_gDeviceAttribute[channel->devType];

	if (devAttr->config.transferType != transferType) {
		return -EINVAL;
	}

	/* Figure out how many descriptors we need. */

	/* printk("srcData: 0x%08x dstData: 0x%08x, numBytes: %d\n", */
	/*        srcData, dstData, numBytes); */

	numDescriptors = dmacHw_calculateDescriptorCount(&devAttr->config,
							      (void *)srcData,
							      (void *)dstData,
							      numBytes);
	if (numDescriptors < 0) {
		printk(KERN_ERR "%s: dmacHw_calculateDescriptorCount failed\n",
		       __func__);
		return -EINVAL;
	}

	/* Check to see if we can reuse the existing descriptor ring, or if we need to allocate */
	/* a new one. */

	ringBytesRequired = dmacHw_descriptorLen(numDescriptors);

	/* printk("ringBytesRequired: %d\n", ringBytesRequired); */

	if (ringBytesRequired > devAttr->ring.bytesAllocated) {
		/* Make sure that this code path is never taken from interrupt context. */
		/* It's OK for an interrupt to initiate a DMA transfer, but the descriptor */
		/* allocation needs to have already been done. */

		might_sleep();

		/* Free the old descriptor ring and allocate a new one. */

		dma_free_descriptor_ring(&devAttr->ring);

		/* And allocate a new one. */

		rc =
		     dma_alloc_descriptor_ring(&devAttr->ring,
					       numDescriptors);
		if (rc < 0) {
			printk(KERN_ERR
			       "%s: dma_alloc_descriptor_ring(%d) failed\n",
			       __func__, numDescriptors);
			return rc;
		}
		/* Setup the descriptor for this transfer */

		if (dmacHw_initDescriptor(devAttr->ring.virtAddr,
					  devAttr->ring.physAddr,
					  devAttr->ring.bytesAllocated,
					  numDescriptors) < 0) {
			printk(KERN_ERR "%s: dmacHw_initDescriptor failed\n",
			       __func__);
			return -EINVAL;
		}
	} else {
		/* We've already got enough ring buffer allocated. All we need to do is reset */
		/* any control information, just in case the previous DMA was stopped. */

		dmacHw_resetDescriptorControl(devAttr->ring.virtAddr);
	}

	/* dma_alloc/free both set the prevSrc/DstData to 0. If they happen to be the same */
	/* as last time, then we don't need to call setDataDescriptor again. */

	if (dmacHw_setDataDescriptor(&devAttr->config,
				     devAttr->ring.virtAddr,
				     (void *)srcData,
				     (void *)dstData, numBytes) < 0) {
		printk(KERN_ERR "%s: dmacHw_setDataDescriptor failed\n",
		       __func__);
		return -EINVAL;
	}

	/* Remember the critical information for this transfer so that we can eliminate */
	/* another call to dma_alloc_descriptors if the caller reuses the same buffers */

	devAttr->prevSrcData = srcData;
	devAttr->prevDstData = dstData;
	devAttr->prevNumBytes = numBytes;

	return 0;
}