| Message ID | 20210312125709.1347177-1-ribalda@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | None | expand |
Hi Ricardo, Thank you for the patch. On Fri, Mar 12, 2021 at 01:57:09PM +0100, Ricardo Ribalda wrote: > On architectures where there is no coherent caching such as ARM use the > dma_alloc_noncontiguous API and handle manually the cache flushing using > dma_sync_sgtable(). You're actually switching to dma_alloc_noncontiguous() unconditionally, not only on those architectures :-) Do I assume correctly that dma_alloc_noncontiguous() will do the right thing on x86 too ? > With this patch on the affected architectures we can measure up to 20x > performance improvement in uvc_video_copy_data_work(). Have you measured performances on x86 to ensure there's no regression ? > Eg: aarch64 with an external usb camera > > NON_CONTIGUOUS > frames: 999 > packets: 999 > empty: 0 (0 %) > errors: 0 > invalid: 0 > pts: 0 early, 0 initial, 999 ok > scr: 0 count ok, 0 diff ok > sof: 2048 <= sof <= 0, freq 0.000 kHz > bytes 67034480 : duration 33303 > FPS: 29.99 > URB: 523446/4993 uS/qty: 104.836 avg 132.532 std 13.230 min 831.094 max (uS) > header: 76564/4993 uS/qty: 15.334 avg 15.229 std 3.438 min 186.875 max (uS) > latency: 468945/4992 uS/qty: 93.939 avg 132.577 std 9.531 min 824.010 max (uS) > decode: 54161/4993 uS/qty: 10.847 avg 6.313 std 1.614 min 111.458 max (uS) > raw decode speed: 9.931 Gbits/s > raw URB handling speed: 1.025 Gbits/s > throughput: 16.102 Mbits/s > URB decode CPU usage 0.162600 % > > COHERENT > frames: 999 > packets: 999 > empty: 0 (0 %) > errors: 0 > invalid: 0 > pts: 0 early, 0 initial, 999 ok > scr: 0 count ok, 0 diff ok > sof: 2048 <= sof <= 0, freq 0.000 kHz > bytes 54683536 : duration 33302 > FPS: 29.99 > URB: 1478135/4000 uS/qty: 369.533 avg 390.357 std 22.968 min 3337.865 max (uS) > header: 79761/4000 uS/qty: 19.940 avg 18.495 std 1.875 min 336.719 max (uS) > latency: 281077/4000 uS/qty: 70.269 avg 83.102 std 5.104 min 735.000 max (uS) > decode: 1197057/4000 uS/qty: 299.264 avg 318.080 std 1.615 min 2806.667 max (uS) > raw decode speed: 365.470 Mbits/s > raw URB handling speed: 295.986 Mbits/s > throughput: 13.136 Mbits/s > URB decode CPU usage 3.594500 % > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org> > Reviewed-by: Tomasz Figa <tfiga@chromium.org> > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > > Changelog from v2: (Thanks Laurent) > > - Fix typos > - Use the right dma direction if not capturing > - Clear sgt during free > > drivers/media/usb/uvc/uvc_video.c | 92 +++++++++++++++++++++++-------- > drivers/media/usb/uvc/uvcvideo.h | 5 +- > 2 files changed, 74 insertions(+), 23 deletions(-) > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > index f2f565281e63..8e60f81e2257 100644 > --- a/drivers/media/usb/uvc/uvc_video.c > +++ b/drivers/media/usb/uvc/uvc_video.c > @@ -6,11 +6,14 @@ > * Laurent Pinchart (laurent.pinchart@ideasonboard.com) > */ > > +#include <linux/dma-mapping.h> > +#include <linux/highmem.h> > #include <linux/kernel.h> > #include <linux/list.h> > #include <linux/module.h> > #include <linux/slab.h> > #include <linux/usb.h> > +#include <linux/usb/hcd.h> > #include <linux/videodev2.h> > #include <linux/vmalloc.h> > #include <linux/wait.h> > @@ -1096,6 +1099,34 @@ static int uvc_video_decode_start(struct uvc_streaming *stream, > return data[0]; > } > > +static inline enum dma_data_direction stream_dir(struct uvc_streaming *stream) > +{ > + if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) > + return DMA_FROM_DEVICE; > + else > + return DMA_TO_DEVICE; > +} > + > +static inline struct device *stream_to_dmadev(struct uvc_streaming *stream) > +{ > + return bus_to_hcd(stream->dev->udev->bus)->self.sysdev; > +} > + > +static void uvc_urb_dma_sync(struct uvc_urb *uvc_urb, bool for_device) Maybe nitpicking a little bit, but wouldn't the code be clearer if you created uvc_urb_dma_sync_for_cpu() and uvc_urb_dma_sync_for_device() ? When reading uvc_urb_dma_sync(uvc_urb, true); I have to constantly look up the definition of the function to figure out what boolean value corresponds to what direction. Given that uvc_urb_dma_sync(..., true) is always called right before submitting the URB, we could even create a uvc_submit_urb() function that groups the dma_sync_sgtable_for_device() and usb_submit_urb() calls, and do without uvc_urb_dma_sync_for_device(). Up to you on this one. With those small changes, and assuming there's no performance regression on x86, Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > +{ > + struct device *dma_dev = stream_to_dmadev(uvc_urb->stream); > + > + if (for_device) { > + dma_sync_sgtable_for_device(dma_dev, uvc_urb->sgt, > + stream_dir(uvc_urb->stream)); > + } else { > + dma_sync_sgtable_for_cpu(dma_dev, uvc_urb->sgt, > + stream_dir(uvc_urb->stream)); > + invalidate_kernel_vmap_range(uvc_urb->buffer, > + uvc_urb->stream->urb_size); > + } > +} > + > /* > * uvc_video_decode_data_work: Asynchronous memcpy processing > * > @@ -1117,6 +1148,8 @@ static void uvc_video_copy_data_work(struct work_struct *work) > uvc_queue_buffer_release(op->buf); > } > > + uvc_urb_dma_sync(uvc_urb, true); > + > ret = usb_submit_urb(uvc_urb->urb, GFP_KERNEL); > if (ret < 0) > dev_err(&uvc_urb->stream->intf->dev, > @@ -1541,10 +1574,12 @@ static void uvc_video_complete(struct urb *urb) > * Process the URB headers, and optionally queue expensive memcpy tasks > * to be deferred to a work queue. > */ > + uvc_urb_dma_sync(uvc_urb, false); > stream->decode(uvc_urb, buf, buf_meta); > > /* If no async work is needed, resubmit the URB immediately. */ > if (!uvc_urb->async_operations) { > + uvc_urb_dma_sync(uvc_urb, true); > ret = usb_submit_urb(uvc_urb->urb, GFP_ATOMIC); > if (ret < 0) > dev_err(&stream->intf->dev, > @@ -1560,24 +1595,49 @@ static void uvc_video_complete(struct urb *urb) > */ > static void uvc_free_urb_buffers(struct uvc_streaming *stream) > { > + struct device *dma_dev = stream_to_dmadev(stream); > struct uvc_urb *uvc_urb; > > for_each_uvc_urb(uvc_urb, stream) { > if (!uvc_urb->buffer) > continue; > > -#ifndef CONFIG_DMA_NONCOHERENT > - usb_free_coherent(stream->dev->udev, stream->urb_size, > - uvc_urb->buffer, uvc_urb->dma); > -#else > - kfree(uvc_urb->buffer); > -#endif > + dma_vunmap_noncontiguous(dma_dev, uvc_urb->buffer); > + dma_free_noncontiguous(dma_dev, stream->urb_size, uvc_urb->sgt, > + stream_dir(stream)); > + > uvc_urb->buffer = NULL; > + uvc_urb->sgt = NULL; > } > > stream->urb_size = 0; > } > > +static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream, > + struct uvc_urb *uvc_urb, gfp_t gfp_flags) > +{ > + struct device *dma_dev = stream_to_dmadev(stream); > + > + uvc_urb->sgt = dma_alloc_noncontiguous(dma_dev, stream->urb_size, > + stream_dir(stream), > + gfp_flags, 0); > + if (!uvc_urb->sgt) > + return false; > + uvc_urb->dma = uvc_urb->sgt->sgl->dma_address; > + > + uvc_urb->buffer = dma_vmap_noncontiguous(dma_dev, stream->urb_size, > + uvc_urb->sgt); > + if (!uvc_urb->buffer) { > + dma_free_noncontiguous(dma_dev, stream->urb_size, > + uvc_urb->sgt, > + stream_dir(stream)); > + uvc_urb->sgt = NULL; > + return false; > + } > + > + return true; > +} > + > /* > * Allocate transfer buffers. This function can be called with buffers > * already allocated when resuming from suspend, in which case it will > @@ -1608,19 +1668,12 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream, > > /* Retry allocations until one succeed. */ > for (; npackets > 1; npackets /= 2) { > + stream->urb_size = psize * npackets; > + > for (i = 0; i < UVC_URBS; ++i) { > struct uvc_urb *uvc_urb = &stream->uvc_urb[i]; > > - stream->urb_size = psize * npackets; > -#ifndef CONFIG_DMA_NONCOHERENT > - uvc_urb->buffer = usb_alloc_coherent( > - stream->dev->udev, stream->urb_size, > - gfp_flags | __GFP_NOWARN, &uvc_urb->dma); > -#else > - uvc_urb->buffer = > - kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN); > -#endif > - if (!uvc_urb->buffer) { > + if (!uvc_alloc_urb_buffer(stream, uvc_urb, gfp_flags)) { > uvc_free_urb_buffers(stream); > break; > } > @@ -1730,12 +1783,8 @@ static int uvc_init_video_isoc(struct uvc_streaming *stream, > urb->context = uvc_urb; > 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 = uvc_urb->dma; > -#else > - urb->transfer_flags = URB_ISO_ASAP; > -#endif > urb->interval = ep->desc.bInterval; > urb->transfer_buffer = uvc_urb->buffer; > urb->complete = uvc_video_complete; > @@ -1795,10 +1844,8 @@ static int uvc_init_video_bulk(struct uvc_streaming *stream, > > usb_fill_bulk_urb(urb, stream->dev->udev, pipe, uvc_urb->buffer, > size, uvc_video_complete, uvc_urb); > -#ifndef CONFIG_DMA_NONCOHERENT > urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP; > urb->transfer_dma = uvc_urb->dma; > -#endif > > uvc_urb->urb = urb; > } > @@ -1895,6 +1942,7 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream, > > /* Submit the URBs. */ > for_each_uvc_urb(uvc_urb, stream) { > + uvc_urb_dma_sync(uvc_urb, true); > ret = usb_submit_urb(uvc_urb->urb, gfp_flags); > if (ret < 0) { > dev_err(&stream->intf->dev, > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h > index 97df5ecd66c9..cce5e38133cd 100644 > --- a/drivers/media/usb/uvc/uvcvideo.h > +++ b/drivers/media/usb/uvc/uvcvideo.h > @@ -219,6 +219,7 @@ > */ > > struct gpio_desc; > +struct sg_table; > struct uvc_device; > > /* TODO: Put the most frequently accessed fields at the beginning of > @@ -545,7 +546,8 @@ struct uvc_copy_op { > * @urb: the URB described by this context structure > * @stream: UVC streaming context > * @buffer: memory storage for the URB > - * @dma: DMA coherent addressing for the urb_buffer > + * @dma: Allocated DMA handle > + * @sgt: sgt_table with the urb locations in memory > * @async_operations: counter to indicate the number of copy operations > * @copy_operations: work descriptors for asynchronous copy operations > * @work: work queue entry for asynchronous decode > @@ -556,6 +558,7 @@ struct uvc_urb { > > char *buffer; > dma_addr_t dma; > + struct sg_table *sgt; > > unsigned int async_operations; > struct uvc_copy_op copy_operations[UVC_MAX_PACKETS];
Hi Laurent Thanks a lot for the review On Fri, Mar 12, 2021 at 10:19 PM Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote: > > Hi Ricardo, > > Thank you for the patch. > > On Fri, Mar 12, 2021 at 01:57:09PM +0100, Ricardo Ribalda wrote: > > On architectures where there is no coherent caching such as ARM use the > > dma_alloc_noncontiguous API and handle manually the cache flushing using > > dma_sync_sgtable(). > > You're actually switching to dma_alloc_noncontiguous() unconditionally, > not only on those architectures :-) Do I assume correctly that > dma_alloc_noncontiguous() will do the right thing on x86 too ? Yes dma_alloc_noncontiguous does all the magic. It falls back to alloc_dma_pages. Christoph has done a great job. I tried it in my notebook and although the images are nothing but pretty it is not the APIs fault. It is because the barbers are closed due to the pandemic ;). > > > With this patch on the affected architectures we can measure up to 20x > > performance improvement in uvc_video_copy_data_work(). > > Have you measured performances on x86 to ensure there's no regression ? Yes in the early stages. I am adding the latest x86 measurements in the commit message in v3 to make it more clear. > > > Eg: aarch64 with an external usb camera > > > > NON_CONTIGUOUS > > frames: 999 > > packets: 999 > > empty: 0 (0 %) > > errors: 0 > > invalid: 0 > > pts: 0 early, 0 initial, 999 ok > > scr: 0 count ok, 0 diff ok > > sof: 2048 <= sof <= 0, freq 0.000 kHz > > bytes 67034480 : duration 33303 > > FPS: 29.99 > > URB: 523446/4993 uS/qty: 104.836 avg 132.532 std 13.230 min 831.094 max (uS) > > header: 76564/4993 uS/qty: 15.334 avg 15.229 std 3.438 min 186.875 max (uS) > > latency: 468945/4992 uS/qty: 93.939 avg 132.577 std 9.531 min 824.010 max (uS) > > decode: 54161/4993 uS/qty: 10.847 avg 6.313 std 1.614 min 111.458 max (uS) > > raw decode speed: 9.931 Gbits/s > > raw URB handling speed: 1.025 Gbits/s > > throughput: 16.102 Mbits/s > > URB decode CPU usage 0.162600 % > > > > COHERENT > > frames: 999 > > packets: 999 > > empty: 0 (0 %) > > errors: 0 > > invalid: 0 > > pts: 0 early, 0 initial, 999 ok > > scr: 0 count ok, 0 diff ok > > sof: 2048 <= sof <= 0, freq 0.000 kHz > > bytes 54683536 : duration 33302 > > FPS: 29.99 > > URB: 1478135/4000 uS/qty: 369.533 avg 390.357 std 22.968 min 3337.865 max (uS) > > header: 79761/4000 uS/qty: 19.940 avg 18.495 std 1.875 min 336.719 max (uS) > > latency: 281077/4000 uS/qty: 70.269 avg 83.102 std 5.104 min 735.000 max (uS) > > decode: 1197057/4000 uS/qty: 299.264 avg 318.080 std 1.615 min 2806.667 max (uS) > > raw decode speed: 365.470 Mbits/s > > raw URB handling speed: 295.986 Mbits/s > > throughput: 13.136 Mbits/s > > URB decode CPU usage 3.594500 % > > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org> > > Reviewed-by: Tomasz Figa <tfiga@chromium.org> > > Signed-off-by: Christoph Hellwig <hch@lst.de> > > --- > > > > Changelog from v2: (Thanks Laurent) > > > > - Fix typos > > - Use the right dma direction if not capturing > > - Clear sgt during free > > > > drivers/media/usb/uvc/uvc_video.c | 92 +++++++++++++++++++++++-------- > > drivers/media/usb/uvc/uvcvideo.h | 5 +- > > 2 files changed, 74 insertions(+), 23 deletions(-) > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > > index f2f565281e63..8e60f81e2257 100644 > > --- a/drivers/media/usb/uvc/uvc_video.c > > +++ b/drivers/media/usb/uvc/uvc_video.c > > @@ -6,11 +6,14 @@ > > * Laurent Pinchart (laurent.pinchart@ideasonboard.com) > > */ > > > > +#include <linux/dma-mapping.h> > > +#include <linux/highmem.h> > > #include <linux/kernel.h> > > #include <linux/list.h> > > #include <linux/module.h> > > #include <linux/slab.h> > > #include <linux/usb.h> > > +#include <linux/usb/hcd.h> > > #include <linux/videodev2.h> > > #include <linux/vmalloc.h> > > #include <linux/wait.h> > > @@ -1096,6 +1099,34 @@ static int uvc_video_decode_start(struct uvc_streaming *stream, > > return data[0]; > > } > > > > +static inline enum dma_data_direction stream_dir(struct uvc_streaming *stream) > > +{ > > + if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) > > + return DMA_FROM_DEVICE; > > + else > > + return DMA_TO_DEVICE; > > +} > > + > > +static inline struct device *stream_to_dmadev(struct uvc_streaming *stream) > > +{ > > + return bus_to_hcd(stream->dev->udev->bus)->self.sysdev; > > +} > > + > > +static void uvc_urb_dma_sync(struct uvc_urb *uvc_urb, bool for_device) > > Maybe nitpicking a little bit, but wouldn't the code be clearer if you > created uvc_urb_dma_sync_for_cpu() and uvc_urb_dma_sync_for_device() ? > When reading > > uvc_urb_dma_sync(uvc_urb, true); > > I have to constantly look up the definition of the function to figure > out what boolean value corresponds to what direction. > > Given that uvc_urb_dma_sync(..., true) is always called right before > submitting the URB, we could even create a uvc_submit_urb() function > that groups the dma_sync_sgtable_for_device() and usb_submit_urb() > calls, and do without uvc_urb_dma_sync_for_device(). Up to you on this > one. I Like it! thanks for the idea > > With those small changes, and assuming there's no performance regression > on x86, How do we take it from here. Christoph merges it from his tree? > > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > > > +{ > > + struct device *dma_dev = stream_to_dmadev(uvc_urb->stream); > > + > > + if (for_device) { > > + dma_sync_sgtable_for_device(dma_dev, uvc_urb->sgt, > > + stream_dir(uvc_urb->stream)); > > + } else { > > + dma_sync_sgtable_for_cpu(dma_dev, uvc_urb->sgt, > > + stream_dir(uvc_urb->stream)); > > + invalidate_kernel_vmap_range(uvc_urb->buffer, > > + uvc_urb->stream->urb_size); > > + } > > +} > > + > > /* > > * uvc_video_decode_data_work: Asynchronous memcpy processing > > * > > @@ -1117,6 +1148,8 @@ static void uvc_video_copy_data_work(struct work_struct *work) > > uvc_queue_buffer_release(op->buf); > > } > > > > + uvc_urb_dma_sync(uvc_urb, true); > > + > > ret = usb_submit_urb(uvc_urb->urb, GFP_KERNEL); > > if (ret < 0) > > dev_err(&uvc_urb->stream->intf->dev, > > @@ -1541,10 +1574,12 @@ static void uvc_video_complete(struct urb *urb) > > * Process the URB headers, and optionally queue expensive memcpy tasks > > * to be deferred to a work queue. > > */ > > + uvc_urb_dma_sync(uvc_urb, false); > > stream->decode(uvc_urb, buf, buf_meta); > > > > /* If no async work is needed, resubmit the URB immediately. */ > > if (!uvc_urb->async_operations) { > > + uvc_urb_dma_sync(uvc_urb, true); > > ret = usb_submit_urb(uvc_urb->urb, GFP_ATOMIC); > > if (ret < 0) > > dev_err(&stream->intf->dev, > > @@ -1560,24 +1595,49 @@ static void uvc_video_complete(struct urb *urb) > > */ > > static void uvc_free_urb_buffers(struct uvc_streaming *stream) > > { > > + struct device *dma_dev = stream_to_dmadev(stream); > > struct uvc_urb *uvc_urb; > > > > for_each_uvc_urb(uvc_urb, stream) { > > if (!uvc_urb->buffer) > > continue; > > > > -#ifndef CONFIG_DMA_NONCOHERENT > > - usb_free_coherent(stream->dev->udev, stream->urb_size, > > - uvc_urb->buffer, uvc_urb->dma); > > -#else > > - kfree(uvc_urb->buffer); > > -#endif > > + dma_vunmap_noncontiguous(dma_dev, uvc_urb->buffer); > > + dma_free_noncontiguous(dma_dev, stream->urb_size, uvc_urb->sgt, > > + stream_dir(stream)); > > + > > uvc_urb->buffer = NULL; > > + uvc_urb->sgt = NULL; > > } > > > > stream->urb_size = 0; > > } > > > > +static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream, > > + struct uvc_urb *uvc_urb, gfp_t gfp_flags) > > +{ > > + struct device *dma_dev = stream_to_dmadev(stream); > > + > > + uvc_urb->sgt = dma_alloc_noncontiguous(dma_dev, stream->urb_size, > > + stream_dir(stream), > > + gfp_flags, 0); > > + if (!uvc_urb->sgt) > > + return false; > > + uvc_urb->dma = uvc_urb->sgt->sgl->dma_address; > > + > > + uvc_urb->buffer = dma_vmap_noncontiguous(dma_dev, stream->urb_size, > > + uvc_urb->sgt); > > + if (!uvc_urb->buffer) { > > + dma_free_noncontiguous(dma_dev, stream->urb_size, > > + uvc_urb->sgt, > > + stream_dir(stream)); > > + uvc_urb->sgt = NULL; > > + return false; > > + } > > + > > + return true; > > +} > > + > > /* > > * Allocate transfer buffers. This function can be called with buffers > > * already allocated when resuming from suspend, in which case it will > > @@ -1608,19 +1668,12 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream, > > > > /* Retry allocations until one succeed. */ > > for (; npackets > 1; npackets /= 2) { > > + stream->urb_size = psize * npackets; > > + > > for (i = 0; i < UVC_URBS; ++i) { > > struct uvc_urb *uvc_urb = &stream->uvc_urb[i]; > > > > - stream->urb_size = psize * npackets; > > -#ifndef CONFIG_DMA_NONCOHERENT > > - uvc_urb->buffer = usb_alloc_coherent( > > - stream->dev->udev, stream->urb_size, > > - gfp_flags | __GFP_NOWARN, &uvc_urb->dma); > > -#else > > - uvc_urb->buffer = > > - kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN); > > -#endif > > - if (!uvc_urb->buffer) { > > + if (!uvc_alloc_urb_buffer(stream, uvc_urb, gfp_flags)) { > > uvc_free_urb_buffers(stream); > > break; > > } > > @@ -1730,12 +1783,8 @@ static int uvc_init_video_isoc(struct uvc_streaming *stream, > > urb->context = uvc_urb; > > 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 = uvc_urb->dma; > > -#else > > - urb->transfer_flags = URB_ISO_ASAP; > > -#endif > > urb->interval = ep->desc.bInterval; > > urb->transfer_buffer = uvc_urb->buffer; > > urb->complete = uvc_video_complete; > > @@ -1795,10 +1844,8 @@ static int uvc_init_video_bulk(struct uvc_streaming *stream, > > > > usb_fill_bulk_urb(urb, stream->dev->udev, pipe, uvc_urb->buffer, > > size, uvc_video_complete, uvc_urb); > > -#ifndef CONFIG_DMA_NONCOHERENT > > urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP; > > urb->transfer_dma = uvc_urb->dma; > > -#endif > > > > uvc_urb->urb = urb; > > } > > @@ -1895,6 +1942,7 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream, > > > > /* Submit the URBs. */ > > for_each_uvc_urb(uvc_urb, stream) { > > + uvc_urb_dma_sync(uvc_urb, true); > > ret = usb_submit_urb(uvc_urb->urb, gfp_flags); > > if (ret < 0) { > > dev_err(&stream->intf->dev, > > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h > > index 97df5ecd66c9..cce5e38133cd 100644 > > --- a/drivers/media/usb/uvc/uvcvideo.h > > +++ b/drivers/media/usb/uvc/uvcvideo.h > > @@ -219,6 +219,7 @@ > > */ > > > > struct gpio_desc; > > +struct sg_table; > > struct uvc_device; > > > > /* TODO: Put the most frequently accessed fields at the beginning of > > @@ -545,7 +546,8 @@ struct uvc_copy_op { > > * @urb: the URB described by this context structure > > * @stream: UVC streaming context > > * @buffer: memory storage for the URB > > - * @dma: DMA coherent addressing for the urb_buffer > > + * @dma: Allocated DMA handle > > + * @sgt: sgt_table with the urb locations in memory > > * @async_operations: counter to indicate the number of copy operations > > * @copy_operations: work descriptors for asynchronous copy operations > > * @work: work queue entry for asynchronous decode > > @@ -556,6 +558,7 @@ struct uvc_urb { > > > > char *buffer; > > dma_addr_t dma; > > + struct sg_table *sgt; > > > > unsigned int async_operations; > > struct uvc_copy_op copy_operations[UVC_MAX_PACKETS]; > > -- > Regards, > > Laurent Pinchart
Hi Ricardo, On Fri, Mar 12, 2021 at 11:15:46PM +0100, Ricardo Ribalda Delgado wrote: > On Fri, Mar 12, 2021 at 10:19 PM Laurent Pinchart wrote: > > On Fri, Mar 12, 2021 at 01:57:09PM +0100, Ricardo Ribalda wrote: > > > On architectures where there is no coherent caching such as ARM use the > > > dma_alloc_noncontiguous API and handle manually the cache flushing using > > > dma_sync_sgtable(). > > > > You're actually switching to dma_alloc_noncontiguous() unconditionally, > > not only on those architectures :-) Do I assume correctly that > > dma_alloc_noncontiguous() will do the right thing on x86 too ? > > Yes dma_alloc_noncontiguous does all the magic. It falls back to > alloc_dma_pages. Christoph has done a great job. It's a really nice work yes. Maybe the commit message could be reworded accordingly then, to explain that we switch to dma_alloc_noncontiguous() unconditionally as it handles the differences behind the scenes ? > I tried it in my notebook and although the images are nothing but > pretty it is not the APIs fault. It is because the barbers are closed > due to the pandemic ;). :-) > > > With this patch on the affected architectures we can measure up to 20x > > > performance improvement in uvc_video_copy_data_work(). > > > > Have you measured performances on x86 to ensure there's no regression ? > > Yes in the early stages. I am adding the latest x86 measurements in > the commit message in v3 to make it more clear. > > > > Eg: aarch64 with an external usb camera > > > > > > NON_CONTIGUOUS > > > frames: 999 > > > packets: 999 > > > empty: 0 (0 %) > > > errors: 0 > > > invalid: 0 > > > pts: 0 early, 0 initial, 999 ok > > > scr: 0 count ok, 0 diff ok > > > sof: 2048 <= sof <= 0, freq 0.000 kHz > > > bytes 67034480 : duration 33303 > > > FPS: 29.99 > > > URB: 523446/4993 uS/qty: 104.836 avg 132.532 std 13.230 min 831.094 max (uS) > > > header: 76564/4993 uS/qty: 15.334 avg 15.229 std 3.438 min 186.875 max (uS) > > > latency: 468945/4992 uS/qty: 93.939 avg 132.577 std 9.531 min 824.010 max (uS) > > > decode: 54161/4993 uS/qty: 10.847 avg 6.313 std 1.614 min 111.458 max (uS) > > > raw decode speed: 9.931 Gbits/s > > > raw URB handling speed: 1.025 Gbits/s > > > throughput: 16.102 Mbits/s > > > URB decode CPU usage 0.162600 % > > > > > > COHERENT > > > frames: 999 > > > packets: 999 > > > empty: 0 (0 %) > > > errors: 0 > > > invalid: 0 > > > pts: 0 early, 0 initial, 999 ok > > > scr: 0 count ok, 0 diff ok > > > sof: 2048 <= sof <= 0, freq 0.000 kHz > > > bytes 54683536 : duration 33302 > > > FPS: 29.99 > > > URB: 1478135/4000 uS/qty: 369.533 avg 390.357 std 22.968 min 3337.865 max (uS) > > > header: 79761/4000 uS/qty: 19.940 avg 18.495 std 1.875 min 336.719 max (uS) > > > latency: 281077/4000 uS/qty: 70.269 avg 83.102 std 5.104 min 735.000 max (uS) > > > decode: 1197057/4000 uS/qty: 299.264 avg 318.080 std 1.615 min 2806.667 max (uS) > > > raw decode speed: 365.470 Mbits/s > > > raw URB handling speed: 295.986 Mbits/s > > > throughput: 13.136 Mbits/s > > > URB decode CPU usage 3.594500 % > > > > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org> > > > Reviewed-by: Tomasz Figa <tfiga@chromium.org> > > > Signed-off-by: Christoph Hellwig <hch@lst.de> > > > --- > > > > > > Changelog from v2: (Thanks Laurent) > > > > > > - Fix typos > > > - Use the right dma direction if not capturing > > > - Clear sgt during free > > > > > > drivers/media/usb/uvc/uvc_video.c | 92 +++++++++++++++++++++++-------- > > > drivers/media/usb/uvc/uvcvideo.h | 5 +- > > > 2 files changed, 74 insertions(+), 23 deletions(-) > > > > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > > > index f2f565281e63..8e60f81e2257 100644 > > > --- a/drivers/media/usb/uvc/uvc_video.c > > > +++ b/drivers/media/usb/uvc/uvc_video.c > > > @@ -6,11 +6,14 @@ > > > * Laurent Pinchart (laurent.pinchart@ideasonboard.com) > > > */ > > > > > > +#include <linux/dma-mapping.h> > > > +#include <linux/highmem.h> > > > #include <linux/kernel.h> > > > #include <linux/list.h> > > > #include <linux/module.h> > > > #include <linux/slab.h> > > > #include <linux/usb.h> > > > +#include <linux/usb/hcd.h> > > > #include <linux/videodev2.h> > > > #include <linux/vmalloc.h> > > > #include <linux/wait.h> > > > @@ -1096,6 +1099,34 @@ static int uvc_video_decode_start(struct uvc_streaming *stream, > > > return data[0]; > > > } > > > > > > +static inline enum dma_data_direction stream_dir(struct uvc_streaming *stream) > > > +{ > > > + if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) > > > + return DMA_FROM_DEVICE; > > > + else > > > + return DMA_TO_DEVICE; > > > +} > > > + > > > +static inline struct device *stream_to_dmadev(struct uvc_streaming *stream) > > > +{ > > > + return bus_to_hcd(stream->dev->udev->bus)->self.sysdev; > > > +} > > > + > > > +static void uvc_urb_dma_sync(struct uvc_urb *uvc_urb, bool for_device) > > > > Maybe nitpicking a little bit, but wouldn't the code be clearer if you > > created uvc_urb_dma_sync_for_cpu() and uvc_urb_dma_sync_for_device() ? > > When reading > > > > uvc_urb_dma_sync(uvc_urb, true); > > > > I have to constantly look up the definition of the function to figure > > out what boolean value corresponds to what direction. > > > > Given that uvc_urb_dma_sync(..., true) is always called right before > > submitting the URB, we could even create a uvc_submit_urb() function > > that groups the dma_sync_sgtable_for_device() and usb_submit_urb() > > calls, and do without uvc_urb_dma_sync_for_device(). Up to you on this > > one. > > I Like it! thanks for the idea > > > > > With those small changes, and assuming there's no performance regression > > on x86, > > How do we take it from here. Christoph merges it from his tree? > > > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > > > > > +{ > > > + struct device *dma_dev = stream_to_dmadev(uvc_urb->stream); > > > + > > > + if (for_device) { > > > + dma_sync_sgtable_for_device(dma_dev, uvc_urb->sgt, > > > + stream_dir(uvc_urb->stream)); > > > + } else { > > > + dma_sync_sgtable_for_cpu(dma_dev, uvc_urb->sgt, > > > + stream_dir(uvc_urb->stream)); > > > + invalidate_kernel_vmap_range(uvc_urb->buffer, > > > + uvc_urb->stream->urb_size); > > > + } > > > +} > > > + > > > /* > > > * uvc_video_decode_data_work: Asynchronous memcpy processing > > > * > > > @@ -1117,6 +1148,8 @@ static void uvc_video_copy_data_work(struct work_struct *work) > > > uvc_queue_buffer_release(op->buf); > > > } > > > > > > + uvc_urb_dma_sync(uvc_urb, true); > > > + > > > ret = usb_submit_urb(uvc_urb->urb, GFP_KERNEL); > > > if (ret < 0) > > > dev_err(&uvc_urb->stream->intf->dev, > > > @@ -1541,10 +1574,12 @@ static void uvc_video_complete(struct urb *urb) > > > * Process the URB headers, and optionally queue expensive memcpy tasks > > > * to be deferred to a work queue. > > > */ > > > + uvc_urb_dma_sync(uvc_urb, false); > > > stream->decode(uvc_urb, buf, buf_meta); > > > > > > /* If no async work is needed, resubmit the URB immediately. */ > > > if (!uvc_urb->async_operations) { > > > + uvc_urb_dma_sync(uvc_urb, true); > > > ret = usb_submit_urb(uvc_urb->urb, GFP_ATOMIC); > > > if (ret < 0) > > > dev_err(&stream->intf->dev, > > > @@ -1560,24 +1595,49 @@ static void uvc_video_complete(struct urb *urb) > > > */ > > > static void uvc_free_urb_buffers(struct uvc_streaming *stream) > > > { > > > + struct device *dma_dev = stream_to_dmadev(stream); > > > struct uvc_urb *uvc_urb; > > > > > > for_each_uvc_urb(uvc_urb, stream) { > > > if (!uvc_urb->buffer) > > > continue; > > > > > > -#ifndef CONFIG_DMA_NONCOHERENT > > > - usb_free_coherent(stream->dev->udev, stream->urb_size, > > > - uvc_urb->buffer, uvc_urb->dma); > > > -#else > > > - kfree(uvc_urb->buffer); > > > -#endif > > > + dma_vunmap_noncontiguous(dma_dev, uvc_urb->buffer); > > > + dma_free_noncontiguous(dma_dev, stream->urb_size, uvc_urb->sgt, > > > + stream_dir(stream)); > > > + > > > uvc_urb->buffer = NULL; > > > + uvc_urb->sgt = NULL; > > > } > > > > > > stream->urb_size = 0; > > > } > > > > > > +static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream, > > > + struct uvc_urb *uvc_urb, gfp_t gfp_flags) > > > +{ > > > + struct device *dma_dev = stream_to_dmadev(stream); > > > + > > > + uvc_urb->sgt = dma_alloc_noncontiguous(dma_dev, stream->urb_size, > > > + stream_dir(stream), > > > + gfp_flags, 0); > > > + if (!uvc_urb->sgt) > > > + return false; > > > + uvc_urb->dma = uvc_urb->sgt->sgl->dma_address; > > > + > > > + uvc_urb->buffer = dma_vmap_noncontiguous(dma_dev, stream->urb_size, > > > + uvc_urb->sgt); > > > + if (!uvc_urb->buffer) { > > > + dma_free_noncontiguous(dma_dev, stream->urb_size, > > > + uvc_urb->sgt, > > > + stream_dir(stream)); > > > + uvc_urb->sgt = NULL; > > > + return false; > > > + } > > > + > > > + return true; > > > +} > > > + > > > /* > > > * Allocate transfer buffers. This function can be called with buffers > > > * already allocated when resuming from suspend, in which case it will > > > @@ -1608,19 +1668,12 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream, > > > > > > /* Retry allocations until one succeed. */ > > > for (; npackets > 1; npackets /= 2) { > > > + stream->urb_size = psize * npackets; > > > + > > > for (i = 0; i < UVC_URBS; ++i) { > > > struct uvc_urb *uvc_urb = &stream->uvc_urb[i]; > > > > > > - stream->urb_size = psize * npackets; > > > -#ifndef CONFIG_DMA_NONCOHERENT > > > - uvc_urb->buffer = usb_alloc_coherent( > > > - stream->dev->udev, stream->urb_size, > > > - gfp_flags | __GFP_NOWARN, &uvc_urb->dma); > > > -#else > > > - uvc_urb->buffer = > > > - kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN); > > > -#endif > > > - if (!uvc_urb->buffer) { > > > + if (!uvc_alloc_urb_buffer(stream, uvc_urb, gfp_flags)) { > > > uvc_free_urb_buffers(stream); > > > break; > > > } > > > @@ -1730,12 +1783,8 @@ static int uvc_init_video_isoc(struct uvc_streaming *stream, > > > urb->context = uvc_urb; > > > 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 = uvc_urb->dma; > > > -#else > > > - urb->transfer_flags = URB_ISO_ASAP; > > > -#endif > > > urb->interval = ep->desc.bInterval; > > > urb->transfer_buffer = uvc_urb->buffer; > > > urb->complete = uvc_video_complete; > > > @@ -1795,10 +1844,8 @@ static int uvc_init_video_bulk(struct uvc_streaming *stream, > > > > > > usb_fill_bulk_urb(urb, stream->dev->udev, pipe, uvc_urb->buffer, > > > size, uvc_video_complete, uvc_urb); > > > -#ifndef CONFIG_DMA_NONCOHERENT > > > urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP; > > > urb->transfer_dma = uvc_urb->dma; > > > -#endif > > > > > > uvc_urb->urb = urb; > > > } > > > @@ -1895,6 +1942,7 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream, > > > > > > /* Submit the URBs. */ > > > for_each_uvc_urb(uvc_urb, stream) { > > > + uvc_urb_dma_sync(uvc_urb, true); > > > ret = usb_submit_urb(uvc_urb->urb, gfp_flags); > > > if (ret < 0) { > > > dev_err(&stream->intf->dev, > > > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h > > > index 97df5ecd66c9..cce5e38133cd 100644 > > > --- a/drivers/media/usb/uvc/uvcvideo.h > > > +++ b/drivers/media/usb/uvc/uvcvideo.h > > > @@ -219,6 +219,7 @@ > > > */ > > > > > > struct gpio_desc; > > > +struct sg_table; > > > struct uvc_device; > > > > > > /* TODO: Put the most frequently accessed fields at the beginning of > > > @@ -545,7 +546,8 @@ struct uvc_copy_op { > > > * @urb: the URB described by this context structure > > > * @stream: UVC streaming context > > > * @buffer: memory storage for the URB > > > - * @dma: DMA coherent addressing for the urb_buffer > > > + * @dma: Allocated DMA handle > > > + * @sgt: sgt_table with the urb locations in memory > > > * @async_operations: counter to indicate the number of copy operations > > > * @copy_operations: work descriptors for asynchronous copy operations > > > * @work: work queue entry for asynchronous decode > > > @@ -556,6 +558,7 @@ struct uvc_urb { > > > > > > char *buffer; > > > dma_addr_t dma; > > > + struct sg_table *sgt; > > > > > > unsigned int async_operations; > > > struct uvc_copy_op copy_operations[UVC_MAX_PACKETS];
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c index f2f565281e63..8e60f81e2257 100644 --- a/drivers/media/usb/uvc/uvc_video.c +++ b/drivers/media/usb/uvc/uvc_video.c @@ -6,11 +6,14 @@ * Laurent Pinchart (laurent.pinchart@ideasonboard.com) */ +#include <linux/dma-mapping.h> +#include <linux/highmem.h> #include <linux/kernel.h> #include <linux/list.h> #include <linux/module.h> #include <linux/slab.h> #include <linux/usb.h> +#include <linux/usb/hcd.h> #include <linux/videodev2.h> #include <linux/vmalloc.h> #include <linux/wait.h> @@ -1096,6 +1099,34 @@ static int uvc_video_decode_start(struct uvc_streaming *stream, return data[0]; } +static inline enum dma_data_direction stream_dir(struct uvc_streaming *stream) +{ + if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) + return DMA_FROM_DEVICE; + else + return DMA_TO_DEVICE; +} + +static inline struct device *stream_to_dmadev(struct uvc_streaming *stream) +{ + return bus_to_hcd(stream->dev->udev->bus)->self.sysdev; +} + +static void uvc_urb_dma_sync(struct uvc_urb *uvc_urb, bool for_device) +{ + struct device *dma_dev = stream_to_dmadev(uvc_urb->stream); + + if (for_device) { + dma_sync_sgtable_for_device(dma_dev, uvc_urb->sgt, + stream_dir(uvc_urb->stream)); + } else { + dma_sync_sgtable_for_cpu(dma_dev, uvc_urb->sgt, + stream_dir(uvc_urb->stream)); + invalidate_kernel_vmap_range(uvc_urb->buffer, + uvc_urb->stream->urb_size); + } +} + /* * uvc_video_decode_data_work: Asynchronous memcpy processing * @@ -1117,6 +1148,8 @@ static void uvc_video_copy_data_work(struct work_struct *work) uvc_queue_buffer_release(op->buf); } + uvc_urb_dma_sync(uvc_urb, true); + ret = usb_submit_urb(uvc_urb->urb, GFP_KERNEL); if (ret < 0) dev_err(&uvc_urb->stream->intf->dev, @@ -1541,10 +1574,12 @@ static void uvc_video_complete(struct urb *urb) * Process the URB headers, and optionally queue expensive memcpy tasks * to be deferred to a work queue. */ + uvc_urb_dma_sync(uvc_urb, false); stream->decode(uvc_urb, buf, buf_meta); /* If no async work is needed, resubmit the URB immediately. */ if (!uvc_urb->async_operations) { + uvc_urb_dma_sync(uvc_urb, true); ret = usb_submit_urb(uvc_urb->urb, GFP_ATOMIC); if (ret < 0) dev_err(&stream->intf->dev, @@ -1560,24 +1595,49 @@ static void uvc_video_complete(struct urb *urb) */ static void uvc_free_urb_buffers(struct uvc_streaming *stream) { + struct device *dma_dev = stream_to_dmadev(stream); struct uvc_urb *uvc_urb; for_each_uvc_urb(uvc_urb, stream) { if (!uvc_urb->buffer) continue; -#ifndef CONFIG_DMA_NONCOHERENT - usb_free_coherent(stream->dev->udev, stream->urb_size, - uvc_urb->buffer, uvc_urb->dma); -#else - kfree(uvc_urb->buffer); -#endif + dma_vunmap_noncontiguous(dma_dev, uvc_urb->buffer); + dma_free_noncontiguous(dma_dev, stream->urb_size, uvc_urb->sgt, + stream_dir(stream)); + uvc_urb->buffer = NULL; + uvc_urb->sgt = NULL; } stream->urb_size = 0; } +static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream, + struct uvc_urb *uvc_urb, gfp_t gfp_flags) +{ + struct device *dma_dev = stream_to_dmadev(stream); + + uvc_urb->sgt = dma_alloc_noncontiguous(dma_dev, stream->urb_size, + stream_dir(stream), + gfp_flags, 0); + if (!uvc_urb->sgt) + return false; + uvc_urb->dma = uvc_urb->sgt->sgl->dma_address; + + uvc_urb->buffer = dma_vmap_noncontiguous(dma_dev, stream->urb_size, + uvc_urb->sgt); + if (!uvc_urb->buffer) { + dma_free_noncontiguous(dma_dev, stream->urb_size, + uvc_urb->sgt, + stream_dir(stream)); + uvc_urb->sgt = NULL; + return false; + } + + return true; +} + /* * Allocate transfer buffers. This function can be called with buffers * already allocated when resuming from suspend, in which case it will @@ -1608,19 +1668,12 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream, /* Retry allocations until one succeed. */ for (; npackets > 1; npackets /= 2) { + stream->urb_size = psize * npackets; + for (i = 0; i < UVC_URBS; ++i) { struct uvc_urb *uvc_urb = &stream->uvc_urb[i]; - stream->urb_size = psize * npackets; -#ifndef CONFIG_DMA_NONCOHERENT - uvc_urb->buffer = usb_alloc_coherent( - stream->dev->udev, stream->urb_size, - gfp_flags | __GFP_NOWARN, &uvc_urb->dma); -#else - uvc_urb->buffer = - kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN); -#endif - if (!uvc_urb->buffer) { + if (!uvc_alloc_urb_buffer(stream, uvc_urb, gfp_flags)) { uvc_free_urb_buffers(stream); break; } @@ -1730,12 +1783,8 @@ static int uvc_init_video_isoc(struct uvc_streaming *stream, urb->context = uvc_urb; 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 = uvc_urb->dma; -#else - urb->transfer_flags = URB_ISO_ASAP; -#endif urb->interval = ep->desc.bInterval; urb->transfer_buffer = uvc_urb->buffer; urb->complete = uvc_video_complete; @@ -1795,10 +1844,8 @@ static int uvc_init_video_bulk(struct uvc_streaming *stream, usb_fill_bulk_urb(urb, stream->dev->udev, pipe, uvc_urb->buffer, size, uvc_video_complete, uvc_urb); -#ifndef CONFIG_DMA_NONCOHERENT urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP; urb->transfer_dma = uvc_urb->dma; -#endif uvc_urb->urb = urb; } @@ -1895,6 +1942,7 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream, /* Submit the URBs. */ for_each_uvc_urb(uvc_urb, stream) { + uvc_urb_dma_sync(uvc_urb, true); ret = usb_submit_urb(uvc_urb->urb, gfp_flags); if (ret < 0) { dev_err(&stream->intf->dev, diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h index 97df5ecd66c9..cce5e38133cd 100644 --- a/drivers/media/usb/uvc/uvcvideo.h +++ b/drivers/media/usb/uvc/uvcvideo.h @@ -219,6 +219,7 @@ */ struct gpio_desc; +struct sg_table; struct uvc_device; /* TODO: Put the most frequently accessed fields at the beginning of @@ -545,7 +546,8 @@ struct uvc_copy_op { * @urb: the URB described by this context structure * @stream: UVC streaming context * @buffer: memory storage for the URB - * @dma: DMA coherent addressing for the urb_buffer + * @dma: Allocated DMA handle + * @sgt: sgt_table with the urb locations in memory * @async_operations: counter to indicate the number of copy operations * @copy_operations: work descriptors for asynchronous copy operations * @work: work queue entry for asynchronous decode @@ -556,6 +558,7 @@ struct uvc_urb { char *buffer; dma_addr_t dma; + struct sg_table *sgt; unsigned int async_operations; struct uvc_copy_op copy_operations[UVC_MAX_PACKETS];