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Subject[PATCH] WIP! media: uvcvideo: Use dma_alloc_noncontiguos API
Date
On architectures where the is no coherent caching such as ARM use the
dma_alloc_noncontiguos API and handle manually the cache flushing using
dma_sync_single().

With this patch on the affected architectures we can measure up to 20x
performance improvement in uvc_video_copy_data_work().

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---

This patch depends on dma_alloc_contiguous API1315351diffmboxseries

https://lore.kernel.org/patchwork/patch/1315351/#1535182

drivers/media/usb/uvc/uvc_video.c | 69 +++++++++++++++++++++++++------
drivers/media/usb/uvc/uvcvideo.h | 1 +
2 files changed, 58 insertions(+), 12 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index ff624bb857d3..ef1b029b8576 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1641,6 +1641,11 @@ static void uvc_video_encode_bulk(struct uvc_urb *uvc_urb,
urb->transfer_buffer_length = stream->urb_size - len;
}

+static inline struct device *stream_to_dmadev(struct uvc_streaming *stream)
+{
+ return stream->dev->udev->bus->controller->parent;
+}
+
static void uvc_video_complete(struct urb *urb)
{
struct uvc_urb *uvc_urb = urb->context;
@@ -1693,6 +1698,11 @@ 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.
*/
+ if (uvc_urb->pages)
+ dma_sync_single_for_cpu(stream_to_dmadev(stream),
+ urb->transfer_dma,
+ urb->transfer_buffer_length,
+ DMA_FROM_DEVICE);
stream->decode(uvc_urb, buf, buf_meta);

/* If no async work is needed, resubmit the URB immediately. */
@@ -1723,8 +1733,15 @@ static void uvc_free_urb_buffers(struct uvc_streaming *stream)
continue;

#ifndef CONFIG_DMA_NONCOHERENT
- usb_free_coherent(stream->dev->udev, stream->urb_size,
- uvc_urb->buffer, uvc_urb->dma);
+ if (uvc_urb->pages) {
+ vunmap(uvc_urb->buffer);
+ dma_free_noncontiguous(stream_to_dmadev(stream),
+ stream->urb_size,
+ uvc_urb->pages, uvc_urb->dma);
+ } else {
+ usb_free_coherent(stream->dev->udev, stream->urb_size,
+ uvc_urb->buffer, uvc_urb->dma);
+ }
#else
kfree(uvc_urb->buffer);
#endif
@@ -1734,6 +1751,42 @@ static void uvc_free_urb_buffers(struct uvc_streaming *stream)
stream->urb_size = 0;
}

+#ifndef CONFIG_DMA_NONCOHERENT
+static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream, struct uvc_urb *uvc_urb,
+ gfp_t gfp_flags)
+{
+ struct device *dma_dev = dma_dev = stream_to_dmadev(stream);
+
+ if (!dma_can_alloc_noncontiguous(dma_dev)) {
+ uvc_urb->buffer = usb_alloc_coherent(stream->dev->udev, stream->urb_size,
+ gfp_flags | __GFP_NOWARN, &uvc_urb->dma);
+ return uvc_urb->buffer != NULL;
+ }
+
+ uvc_urb->pages = dma_alloc_noncontiguous(dma_dev, stream->urb_size,
+ &uvc_urb->dma, gfp_flags | __GFP_NOWARN, 0);
+ if (!uvc_urb->pages)
+ return false;
+
+ uvc_urb->buffer = vmap(uvc_urb->pages, PAGE_ALIGN(stream->urb_size) >> PAGE_SHIFT,
+ VM_DMA_COHERENT, PAGE_KERNEL);
+ if (!uvc_urb->buffer) {
+ dma_free_noncontiguous(dma_dev, stream->urb_size, uvc_urb->pages, uvc_urb->dma);
+ return false;
+ }
+
+ return true;
+}
+#else
+static bool uvc_alloc_urb_buffer(struct uvc_streaming *stream, struct uvc_urb *uvc_urb,
+ gfp_t gfp_flags)
+{
+ uvc_urb->buffer = kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN);
+
+ return uvc_urb->buffer != NULL;
+}
+#endif
+
/*
* Allocate transfer buffers. This function can be called with buffers
* already allocated when resuming from suspend, in which case it will
@@ -1764,19 +1817,11 @@ 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;
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;
}
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 60d830d74ac1..80eeeaf3cd06 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -544,6 +544,7 @@ struct uvc_urb {

char *buffer;
dma_addr_t dma;
+ struct page **pages;

unsigned int async_operations;
struct uvc_copy_op copy_operations[UVC_MAX_PACKETS];
--
2.29.2.299.gdc1121823c-goog
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