Hi Al,
Thanks for the patch.
On Thursday 18 August 2011 15:28:29 Al Cooper wrote:
> The UVC driver uses usb_alloc_coherent() to allocate DMA data buffers.
> On systems without coherent DMA this ends up allocating buffers in
> uncached memory. The subsequent memcpy's done to coalesce the DMA
> chunks into contiguous buffers then run VERY slowly. On a MIPS test
> system the memcpy is about 200 times slower. This issue prevents the
> system from keeping up with 720p YUYV data at 10fps.
>
> The following patch uses kmalloc to alloc the DMA buffers instead of
> uab_alloc_coherent on systems without coherent DMA. With this patch
> the system was easily able to keep up with 720p at 10fps.
>
> Signed-off-by: Al Cooper <alcooperx@xxxxxxxxx>
Acked-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
I will push it to v3.2.
> ---
> drivers/media/video/uvc/uvc_video.c | 18 +++++++++++++++++-
> 1 files changed, 17 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/media/video/uvc/uvc_video.c
> b/drivers/media/video/uvc/uvc_video.c index 4999479..30c18b4 100644
> --- a/drivers/media/video/uvc/uvc_video.c
> +++ b/drivers/media/video/uvc/uvc_video.c
> @@ -790,8 +790,12 @@ static void uvc_free_urb_buffers(struct uvc_streaming
> *stream)
>
> for (i = 0; i < UVC_URBS; ++i) {
> if (stream->urb_buffer[i]) {
> +#ifndef CONFIG_DMA_NONCOHERENT
> usb_free_coherent(stream->dev->udev, stream->urb_size,
> stream->urb_buffer[i], stream->urb_dma[i]);
> +#else
> + kfree(stream->urb_buffer[i]);
> +#endif
> stream->urb_buffer[i] = NULL;
> }
> }
> @@ -831,9 +835,15 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming
> *stream, for (; npackets > 1; npackets /= 2) {
> for (i = 0; i < UVC_URBS; ++i) {
> stream->urb_size = psize * npackets;
> +#ifndef CONFIG_DMA_NONCOHERENT
> stream->urb_buffer[i] = usb_alloc_coherent(
> stream->dev->udev, stream->urb_size,
> gfp_flags | __GFP_NOWARN, &stream->urb_dma[i]);
> +#else
> + stream->urb_buffer[i] =
> + kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN);
> +#endif
> +
> if (!stream->urb_buffer[i]) {
> uvc_free_urb_buffers(stream);
> break;
> @@ -908,10 +918,14 @@ static int uvc_init_video_isoc(struct uvc_streaming
> *stream, urb->context = stream;
> urb->pipe = usb_rcvisocpipe(stream->dev->udev,
> ep->desc.bEndpointAddress);
> +#ifndef CONFIG_DMA_NONCOHERENT
> urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
> + urb->transfer_dma = stream->urb_dma[i];
> +#else
> + urb->transfer_flags = URB_ISO_ASAP;
> +#endif
> urb->interval = ep->desc.bInterval;
> urb->transfer_buffer = stream->urb_buffer[i];
> - urb->transfer_dma = stream->urb_dma[i];
> urb->complete = uvc_video_complete;
> urb->number_of_packets = npackets;
> urb->transfer_buffer_length = size;
> @@ -969,8 +983,10 @@ static int uvc_init_video_bulk(struct uvc_streaming
> *stream, usb_fill_bulk_urb(urb, stream->dev->udev, pipe,
> stream->urb_buffer[i], size, uvc_video_complete,
> stream);
> +#ifndef CONFIG_DMA_NONCOHERENT
> urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
> urb->transfer_dma = stream->urb_dma[i];
> +#endif
>
> stream->urb[i] = urb;
> }
--
Regards,
Laurent Pinchart
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