media: uvcvideo: Use dma_alloc_noncontiguous API

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().

If the architechture has coherent cache, the API falls back to
alloc_dma_pages, so we can remove the coherent caching code-path from the
driver, making it simpler.

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 %

In non-affected architectures we see no significant impact.

Eg: x86 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 70179056 : duration 33301
FPS: 29.99
URB: 288901/4897 uS/qty: 58.995 avg 26.022 std 4.319 min 253.853 max (uS)
header: 54792/4897 uS/qty: 11.189 avg 6.218 std 0.620 min 61.750 max (uS)
latency: 236602/4897 uS/qty: 48.315 avg 24.244 std 1.764 min 240.924 max (uS)
decode: 52298/4897 uS/qty: 10.679 avg 8.299 std 1.638 min 108.861 max (uS)
raw decode speed: 10.796 Gbits/s
raw URB handling speed: 1.949 Gbits/s
throughput: 16.859 Mbits/s
URB decode CPU usage 0.157000 %

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 71818320 : duration 33301
FPS: 29.99
URB: 321021/5000 uS/qty: 64.204 avg 23.001 std 10.430 min 268.837 max (uS)
header: 54308/5000 uS/qty: 10.861 avg 5.104 std 0.778 min 54.736 max (uS)
latency: 268799/5000 uS/qty: 53.759 avg 21.827 std 6.095 min 255.153 max (uS)
decode: 52222/5000 uS/qty: 10.444 avg 7.137 std 1.874 min 71.103 max (uS)
raw decode speed: 11.048 Gbits/s
raw URB handling speed: 1.789 Gbits/s
throughput: 17.253 Mbits/s
URB decode CPU usage 0.156800 %

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

2 files changed, 73 insertions, 26 deletions

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index f2f565281e63..a777b389a66e 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 +1099,29 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
 	return data[0];
 }
 
+static inline enum dma_data_direction uvc_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 *uvc_stream_to_dmadev(struct uvc_streaming *stream)
+{
+	return bus_to_hcd(stream->dev->udev->bus)->self.sysdev;
+}
+
+static int uvc_submit_urb(struct uvc_urb *uvc_urb, gfp_t mem_flags)
+{
+	/* Sync DMA. */
+	dma_sync_sgtable_for_device(uvc_stream_to_dmadev(uvc_urb->stream),
+				    uvc_urb->sgt,
+				    uvc_stream_dir(uvc_urb->stream));
+	return usb_submit_urb(uvc_urb->urb, mem_flags);
+}
+
 /*
  * uvc_video_decode_data_work: Asynchronous memcpy processing
  *
@@ -1117,7 +1143,7 @@ static void uvc_video_copy_data_work(struct work_struct *work)
 		uvc_queue_buffer_release(op->buf);
 	}
 
-	ret = usb_submit_urb(uvc_urb->urb, GFP_KERNEL);
+	ret = uvc_submit_urb(uvc_urb, GFP_KERNEL);
 	if (ret < 0)
 		dev_err(&uvc_urb->stream->intf->dev,
 			"Failed to resubmit video URB (%d).\n", ret);
@@ -1537,6 +1563,12 @@ static void uvc_video_complete(struct urb *urb)
 	/* Re-initialise the URB async work. */
 	uvc_urb->async_operations = 0;
 
+	/* Sync DMA and invalidate vmap range. */
+	dma_sync_sgtable_for_cpu(uvc_stream_to_dmadev(uvc_urb->stream),
+				 uvc_urb->sgt, uvc_stream_dir(stream));
+	invalidate_kernel_vmap_range(uvc_urb->buffer,
+				     uvc_urb->stream->urb_size);
+
 	/*
 	 * Process the URB headers, and optionally queue expensive memcpy tasks
 	 * to be deferred to a work queue.
@@ -1545,7 +1577,7 @@ static void uvc_video_complete(struct urb *urb)
 
 	/* If no async work is needed, resubmit the URB immediately. */
 	if (!uvc_urb->async_operations) {
-		ret = usb_submit_urb(uvc_urb->urb, GFP_ATOMIC);
+		ret = uvc_submit_urb(uvc_urb, GFP_ATOMIC);
 		if (ret < 0)
 			dev_err(&stream->intf->dev,
 				"Failed to resubmit video URB (%d).\n", ret);
@@ -1560,24 +1592,49 @@ static void uvc_video_complete(struct urb *urb)
  */
 static void uvc_free_urb_buffers(struct uvc_streaming *stream)
 {
+	struct device *dma_dev = uvc_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_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 = uvc_stream_to_dmadev(stream);
+
+	uvc_urb->sgt = dma_alloc_noncontiguous(dma_dev, stream->urb_size,
+					       uvc_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,
+				       uvc_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 +1665,12 @@ 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 +1780,8 @@ 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 +1841,8 @@ 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;
 	}
@@ -1895,7 +1939,7 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
 
 	/* Submit the URBs. */
 	for_each_uvc_urb(uvc_urb, stream) {
-		ret = usb_submit_urb(uvc_urb->urb, gfp_flags);
+		ret = uvc_submit_urb(uvc_urb, gfp_flags);
 		if (ret < 0) {
 			dev_err(&stream->intf->dev,
 				"Failed to submit URB %u (%d).\n",
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];