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_sgtable().
With this patch on the affected architectures we can measure up to 20x
performance improvement in uvc_video_copy_data_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@xxxxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
v2:
- Replace DMA_BIDIRECTIONAL with DMA_FROM_DEVICE
- Add invalidate_kernel_vmap_range
- Tested in an X86 notebook and an ARM Chromebook
drivers/media/usb/uvc/uvc_video.c | 80 ++++++++++++++++++++++---------
drivers/media/usb/uvc/uvcvideo.h | 4 +-
2 files changed, 61 insertions(+), 23 deletions(-)
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index a6a441d92b94..378fb5f29920 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@xxxxxxxxxxxxxxxx)
*/
+#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>
@@ -1097,6 +1099,26 @@ 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 = dma_dev = stream_to_dmadev(uvc_urb->stream);
+
+ if (for_device) {
+ dma_sync_sgtable_for_device(dma_dev, uvc_urb->sgt,
+ DMA_FROM_DEVICE);
+ } 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
*
@@ -1118,6 +1140,8 @@ 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)
uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",
@@ -1539,10 +1563,12 @@ 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)
uvc_printk(KERN_ERR,
@@ -1559,24 +1585,47 @@ static void uvc_video_complete(struct urb *urb)
*/
static void uvc_free_urb_buffers(struct uvc_streaming *stream)
{
+ struct device *dma_dev = 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,
+ uvc_urb->dma, DMA_FROM_DEVICE);
+
uvc_urb->buffer = 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,
+ &uvc_urb->dma, DMA_FROM_DEVICE,
+ gfp_flags);
+ if (!uvc_urb->sgt)
+ return false;
+
+ 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, uvc_urb->dma,
+ DMA_FROM_DEVICE);
+ 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
@@ -1607,19 +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;
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;
}
@@ -1728,12 +1769,8 @@ 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;
@@ -1793,10 +1830,8 @@ 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;
}
@@ -1891,6 +1926,7 @@ 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) {
uvc_printk(KERN_ERR, "Failed to submit URB %u (%d).\n",
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index a3dfacf069c4..a386114bd229 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -521,7 +521,8 @@ 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
@@ -532,6 +533,7 @@ 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];
--
2.30.0.280.ga3ce27912f-goog
