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    SubjectRe: [PATCH 6/6] media: uvcvideo: Use dma_alloc_noncontiguos API
    And I forgot to mention:

    On Fri, Mar 12, 2021 at 03:42:14AM +0200, Laurent Pinchart wrote:
    > Hi Christoph and Ricardo,
    >
    > Thank you for the patch.
    >
    > On Mon, Mar 01, 2021 at 09:52:36AM +0100, Christoph Hellwig wrote:
    > > From: Ricardo Ribalda <ribalda@chromium.org>
    > >
    > > On architectures where the is no coherent caching such as ARM use the
    >
    > s/the is/there is/
    >
    > > dma_alloc_noncontiguos API and handle manually the cache flushing using
    >
    > s/dma_alloc_noncontiguos/dma_alloc_noncontiguous/
    >
    > (and in the subject line too)
    >
    > > dma_sync_sgtable().
    > >
    > > With this patch on the affected architectures we can measure up to 20x
    > > performance improvement in uvc_video_copy_data_work().

    Wow, great work ! :-)

    > >
    > > 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>
    > > ---
    > > drivers/media/usb/uvc/uvc_video.c | 79 ++++++++++++++++++++++---------
    > > drivers/media/usb/uvc/uvcvideo.h | 4 +-
    > > 2 files changed, 60 insertions(+), 23 deletions(-)
    > >
    > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
    > > index f2f565281e63ff..d008c68fb6c806 100644
    > > --- a/drivers/media/usb/uvc/uvc_video.c
    > > +++ b/drivers/media/usb/uvc/uvc_video.c
    > > @@ -6,11 +6,13 @@
    > > * Laurent Pinchart (laurent.pinchart@ideasonboard.com)
    > > */
    > >
    >
    > Should we 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 +1098,26 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
    > > return data[0];
    > > }
    > >
    > > +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,
    > > + DMA_FROM_DEVICE);
    >
    > The uvcvideo driver also supports video output devices (they are fairly
    > rare, but they exist). We thus need to handle DMA_TO_DEVICE too.
    >
    > > + } else {
    > > + dma_sync_sgtable_for_cpu(dma_dev, uvc_urb->sgt,
    > > + DMA_FROM_DEVICE);
    > > + invalidate_kernel_vmap_range(uvc_urb->buffer,
    > > + uvc_urb->stream->urb_size);
    > > + }
    > > +}
    > > +
    > > /*
    > > * uvc_video_decode_data_work: Asynchronous memcpy processing
    > > *
    > > @@ -1117,6 +1139,8 @@ 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 +1565,12 @@ 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 +1586,46 @@ 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,
    > > + DMA_FROM_DEVICE);
    > > +
    > > uvc_urb->buffer = NULL;
    >
    > Maybe also
    >
    > uvc_urb->sgt = NULL;
    >
    > ? It's not strictly mandatory, but may make use-after-free bugs easier
    > to spot.
    >
    > > }
    > >
    > > 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);
    > > +
    > > +
    >
    > Extra blank line.
    >
    > > + uvc_urb->sgt = dma_alloc_noncontiguous(dma_dev, stream->urb_size,
    > > + DMA_FROM_DEVICE, 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, DMA_FROM_DEVICE);
    >
    > Same here,
    >
    > 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 +1656,11 @@ 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;
    >
    > A blank line here would be nice.
    >
    > > 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 +1770,8 @@ 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 +1831,8 @@ 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 +1929,7 @@ 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 97df5ecd66c9a7..fec24f1eca1c96 100644
    > > --- a/drivers/media/usb/uvc/uvcvideo.h
    > > +++ b/drivers/media/usb/uvc/uvcvideo.h
    > > @@ -545,7 +545,8 @@ 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 +557,7 @@ struct uvc_urb {
    > >
    > > char *buffer;
    > > dma_addr_t dma;
    > > + struct sg_table *sgt;
    >
    > A forward declaration of struct sg_table with the other forward
    > declarations would be useful.
    >
    > >
    > > unsigned int async_operations;
    > > struct uvc_copy_op copy_operations[UVC_MAX_PACKETS];

    --
    Regards,

    Laurent Pinchart

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