From 3e0ac6717b0a2593243ef3850025a42cb199880f Mon Sep 17 00:00:00 2001 From: Al Cooper Date: Thu, 18 Aug 2011 10:28:29 -0300 Subject: [PATCH] [media] media: Fix a UVC performance problem on systems with non-coherent DMA 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 usb_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 Acked-by: Laurent Pinchart Signed-off-by: Mauro Carvalho Chehab --- drivers/media/video/uvc/uvc_video.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/media/video/uvc/uvc_video.c b/drivers/media/video/uvc/uvc_video.c index ffd1158628b6..b015e8e5e8b0 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 +835,14 @@ 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 +917,14 @@ 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 +982,10 @@ 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; } -- 2.34.1