[media] cx231xx: use URB_NO_TRANSFER_DMA_MAP on URBs allocated with usb_alloc_urb()

URBs allocated with usb_alloc_urb() are allocated from DMA-coherent
areas, and therefore it is not necessary to call dma_map_single() on
such buffers. Worst, on ARM, calling dma_map_single() on a
DMA-coherent buffer will trigger a BUG_ON() in
arch/arm/mm/dma-mapping.c.

Therefore, we mark all URBs allocated with usb_alloc_urb() with the
URB_NO_TRANSFER_DMA_MAP transfer_flags, so that the USB core does not
do dma_map_single()/dma_unmap_single() on those buffers.

This is similar to 882787ff for the
gspca driver, and has already been discussed on the linux-media list
in the past:
http://www.mail-archive.com/linux-media@vger.kernel.org/msg37086.html.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/cx231xx/cx231xx-audio.c

@@ -307,7 +307,7 @@ static int cx231xx_init_audio_isoc(struct cx231xx *dev)
 		urb->context = dev;
 		urb->pipe = usb_rcvisocpipe(dev->udev,
 						dev->adev.end_point_addr);
-		urb->transfer_flags = URB_ISO_ASAP;
+		urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
 		urb->transfer_buffer = dev->adev.transfer_buffer[i];
 		urb->interval = 1;
 		urb->complete = cx231xx_audio_isocirq;
@@ -368,7 +368,7 @@ static int cx231xx_init_audio_bulk(struct cx231xx *dev)
 		urb->context = dev;
 		urb->pipe = usb_rcvbulkpipe(dev->udev,
 						dev->adev.end_point_addr);
-		urb->transfer_flags = 0;
+		urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
 		urb->transfer_buffer = dev->adev.transfer_buffer[i];
 		urb->complete = cx231xx_audio_bulkirq;
 		urb->transfer_buffer_length = sb_size;

drivers/media/video/cx231xx/cx231xx-core.c

@@ -1074,7 +1074,7 @@ int cx231xx_init_isoc(struct cx231xx *dev, int max_packets,
 				 sb_size, cx231xx_isoc_irq_callback, dma_q, 1);
 
 		urb->number_of_packets = max_packets;
-		urb->transfer_flags = URB_ISO_ASAP;
+		urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
 
 		k = 0;
 		for (j = 0; j < max_packets; j++) {
@@ -1185,7 +1185,7 @@ int cx231xx_init_bulk(struct cx231xx *dev, int max_packets,
 			return -ENOMEM;
 		}
 		dev->video_mode.bulk_ctl.urb[i] = urb;
-		urb->transfer_flags = 0;
+		urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
 
 		dev->video_mode.bulk_ctl.transfer_buffer[i] =
 		    usb_alloc_coherent(dev->udev, sb_size, GFP_KERNEL,

drivers/media/video/cx231xx/cx231xx-vbi.c

@@ -452,7 +452,7 @@ int cx231xx_init_vbi_isoc(struct cx231xx *dev, int max_packets,
 			return -ENOMEM;
 		}
 		dev->vbi_mode.bulk_ctl.urb[i] = urb;
-		urb->transfer_flags = 0;
+		urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
 
 		dev->vbi_mode.bulk_ctl.transfer_buffer[i] =
 		    kzalloc(sb_size, GFP_KERNEL);