[PATCH v2 0/5] usb: gadget: uvc: improve uvc gadget performance

[PATCH v2 0/5] usb: gadget: uvc: improve uvc gadget performance

[Michael Grzeschik]

This series improves the performance of the uvc video gadget by adding a
zero copy routine using the scatter list interface of the gadget. The
series also increases the amount of allocated requests depending of the
speed and it also reduces the interrupt load by only trigger on every
16th request in case of super-speed.

Michael Grzeschik (5):
  usb: dwc3: gadget: set gadgets parent to the right controller
  usb: gadget: uvc: make uvc_num_requests depend on gadget speed
  usb: gadget: uvc: set v4l2_dev->dev in f_uvc
  usb: gadget: uvc: add scatter gather support
  usb: gadget: uvc: decrease the interrupt load to a quarter

 drivers/usb/dwc3/gadget.c               |   2 +-
 drivers/usb/gadget/Kconfig              |   1 +
 drivers/usb/gadget/function/f_uvc.c     |   1 +
 drivers/usb/gadget/function/uvc.h       |  15 ++-
 drivers/usb/gadget/function/uvc_queue.c |  28 ++++-
 drivers/usb/gadget/function/uvc_queue.h |   7 +-
 drivers/usb/gadget/function/uvc_video.c | 155 +++++++++++++++++++-----
 drivers/usb/gadget/legacy/Kconfig       |   1 +
 8 files changed, 175 insertions(+), 35 deletions(-)

-- 
2.30.2

[PATCH v2 1/5] usb: dwc3: gadget: set gadgets parent to the right controller

[Michael Grzeschik]

In case of dwc3 it is possible that the sysdev is the parent of the
controller. To ensure the right dev is set to the gadget's dev parent we
will hand over sysdev instead of dev, which will always point to the
controller.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

---
v2: first version of patch

---
 drivers/usb/dwc3/gadget.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index af6d7f157989d..8a1b1daff2e97 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -3990,7 +3990,7 @@ int dwc3_gadget_init(struct dwc3 *dwc)
 	}
 
 
-	usb_initialize_gadget(dwc->dev, dwc->gadget, dwc_gadget_release);
+	usb_initialize_gadget(dwc->sysdev, dwc->gadget, dwc_gadget_release);
 	dev				= &dwc->gadget->dev;
 	dev->platform_data		= dwc;
 	dwc->gadget->ops		= &dwc3_gadget_ops;
-- 
2.30.2

[PATCH v2 2/5] usb: gadget: uvc: make uvc_num_requests depend on gadget speed

[Michael Grzeschik]

While sending bigger images is possible with USB_SPEED_SUPER it is
better to use more isochronous requests in flight. This patch makes the
number uvc_num_requests dynamic by changing it depending on the gadget
speed.

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

---
v1 -> v2: - using u8 instead of __u8
          - made uvc_num_requests usigned int
	  - directly referencing usb_composite_dev
	  - removed extra include module.h
	  - formated coding style
	  - returning -ENOMEM on alloc error

---
 drivers/usb/gadget/function/uvc.h       | 11 +++--
 drivers/usb/gadget/function/uvc_queue.c |  6 +++
 drivers/usb/gadget/function/uvc_video.c | 55 +++++++++++++++----------
 3 files changed, 47 insertions(+), 25 deletions(-)

diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 23ee25383c1f7..52f894183ecf0 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -65,13 +65,17 @@ extern unsigned int uvc_gadget_trace_param;
  * Driver specific constants
  */
 
-#define UVC_NUM_REQUESTS			4
 #define UVC_MAX_REQUEST_SIZE			64
 #define UVC_MAX_EVENTS				4
 
 /* ------------------------------------------------------------------------
  * Structures
  */
+struct uvc_request {
+	struct usb_request *req;
+	u8 *req_buffer;
+	struct uvc_video *video;
+};
 
 struct uvc_video {
 	struct uvc_device *uvc;
@@ -87,10 +91,11 @@ struct uvc_video {
 	unsigned int imagesize;
 	struct mutex mutex;	/* protects frame parameters */
 
+	unsigned int uvc_num_requests;
+
 	/* Requests */
 	unsigned int req_size;
-	struct usb_request *req[UVC_NUM_REQUESTS];
-	__u8 *req_buffer[UVC_NUM_REQUESTS];
+	struct uvc_request *ureq;
 	struct list_head req_free;
 	spinlock_t req_lock;
 
diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index 61e2c94cc0b0c..ff0cc08531d2b 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -43,6 +43,7 @@ static int uvc_queue_setup(struct vb2_queue *vq,
 {
 	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
 	struct uvc_video *video = container_of(queue, struct uvc_video, queue);
+	struct usb_composite_dev *cdev = video->uvc->func.config->cdev;
 
 	if (*nbuffers > UVC_MAX_VIDEO_BUFFERS)
 		*nbuffers = UVC_MAX_VIDEO_BUFFERS;
@@ -51,6 +52,11 @@ static int uvc_queue_setup(struct vb2_queue *vq,
 
 	sizes[0] = video->imagesize;
 
+	if (cdev->gadget->speed < USB_SPEED_SUPER)
+		video->uvc_num_requests = 4;
+	else
+		video->uvc_num_requests = 64;
+
 	return 0;
 }
 
diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 633e23d58d868..303cb427f687e 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -145,7 +145,8 @@ static int uvcg_video_ep_queue(struct uvc_video *video, struct usb_request *req)
 static void
 uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
 {
-	struct uvc_video *video = req->context;
+	struct uvc_request *ureq = req->context;
+	struct uvc_video *video = ureq->video;
 	struct uvc_video_queue *queue = &video->queue;
 	unsigned long flags;
 
@@ -177,16 +178,21 @@ uvc_video_free_requests(struct uvc_video *video)
 {
 	unsigned int i;
 
-	for (i = 0; i < UVC_NUM_REQUESTS; ++i) {
-		if (video->req[i]) {
-			usb_ep_free_request(video->ep, video->req[i]);
-			video->req[i] = NULL;
+	if (video->ureq) {
+		for (i = 0; i < video->uvc_num_requests; ++i) {
+			if (video->ureq[i].req) {
+				usb_ep_free_request(video->ep, video->ureq[i].req);
+				video->ureq[i].req = NULL;
+			}
+
+			if (video->ureq[i].req_buffer) {
+				kfree(video->ureq[i].req_buffer);
+				video->ureq[i].req_buffer = NULL;
+			}
 		}
 
-		if (video->req_buffer[i]) {
-			kfree(video->req_buffer[i]);
-			video->req_buffer[i] = NULL;
-		}
+		kfree(video->ureq);
+		video->ureq = NULL;
 	}
 
 	INIT_LIST_HEAD(&video->req_free);
@@ -207,21 +213,26 @@ uvc_video_alloc_requests(struct uvc_video *video)
 		 * max_t(unsigned int, video->ep->maxburst, 1)
 		 * (video->ep->mult);
 
-	for (i = 0; i < UVC_NUM_REQUESTS; ++i) {
-		video->req_buffer[i] = kmalloc(req_size, GFP_KERNEL);
-		if (video->req_buffer[i] == NULL)
+	video->ureq = kcalloc(video->uvc_num_requests, sizeof(struct uvc_request), GFP_KERNEL);
+	if (video->ureq == NULL)
+		return -ENOMEM;
+
+	for (i = 0; i < video->uvc_num_requests; ++i) {
+		video->ureq[i].req_buffer = kmalloc(req_size, GFP_KERNEL);
+		if (video->ureq[i].req_buffer == NULL)
 			goto error;
 
-		video->req[i] = usb_ep_alloc_request(video->ep, GFP_KERNEL);
-		if (video->req[i] == NULL)
+		video->ureq[i].req = usb_ep_alloc_request(video->ep, GFP_KERNEL);
+		if (video->ureq[i].req == NULL)
 			goto error;
 
-		video->req[i]->buf = video->req_buffer[i];
-		video->req[i]->length = 0;
-		video->req[i]->complete = uvc_video_complete;
-		video->req[i]->context = video;
+		video->ureq[i].req->buf = video->ureq[i].req_buffer;
+		video->ureq[i].req->length = 0;
+		video->ureq[i].req->complete = uvc_video_complete;
+		video->ureq[i].req->context = &video->ureq[i];
+		video->ureq[i].video = video;
 
-		list_add_tail(&video->req[i]->list, &video->req_free);
+		list_add_tail(&video->ureq[i].req->list, &video->req_free);
 	}
 
 	video->req_size = req_size;
@@ -312,9 +323,9 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
 		cancel_work_sync(&video->pump);
 		uvcg_queue_cancel(&video->queue, 0);
 
-		for (i = 0; i < UVC_NUM_REQUESTS; ++i)
-			if (video->req[i])
-				usb_ep_dequeue(video->ep, video->req[i]);
+		for (i = 0; i < video->uvc_num_requests; ++i)
+			if (video->ureq && video->ureq[i].req)
+				usb_ep_dequeue(video->ep, video->ureq[i].req);
 
 		uvc_video_free_requests(video);
 		uvcg_queue_enable(&video->queue, 0);
-- 
2.30.2

[PATCH v2 3/5] usb: gadget: uvc: set v4l2_dev->dev in f_uvc

[Michael Grzeschik]

The v4l2_dev has no corresponding device to it. We will
point it to the gadget's dev.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

---
v1 -> v2: Extracted from previous bigger patch

---
 drivers/usb/gadget/function/f_uvc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index f48a00e497945..9d87c0fb8f92e 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -418,6 +418,7 @@ uvc_register_video(struct uvc_device *uvc)
 
 	/* TODO reference counting. */
 	uvc->vdev.v4l2_dev = &uvc->v4l2_dev;
+	uvc->vdev.v4l2_dev->dev = &cdev->gadget->dev;
 	uvc->vdev.fops = &uvc_v4l2_fops;
 	uvc->vdev.ioctl_ops = &uvc_v4l2_ioctl_ops;
 	uvc->vdev.release = video_device_release_empty;
-- 
2.30.2

[PATCH v2 4/5] usb: gadget: uvc: add scatter gather support

[Michael Grzeschik]

This patch adds support for scatter gather transfers. If the underlying
gadgets sg_supported == true, then the videeobuf2-dma-sg is used and the
encode routine maps all scatter entries to separate scatterlists for the
usb gadget.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

---
v1 -> v2: - fixed missing VIDEOBUF2_DMA_SG select for legacy webcam found by kbuild-all
	  - ordered header files alphabetically
	  - changed function parameter order in uvcg_queue_init
	  - used unsigned int in encode_isoc_sg where possible
          - added and used UVCG_REQUEST_HEADER_LEN for the 2 header bytes
	  - added use_sg into uvc_video_queue instead of pocking through layers
	  - added sg_free_table to uvc_video_free_requests
	  - removed unneeded memset

---
 drivers/usb/gadget/Kconfig              |  1 +
 drivers/usb/gadget/function/uvc.h       |  2 +
 drivers/usb/gadget/function/uvc_queue.c | 22 ++++++-
 drivers/usb/gadget/function/uvc_queue.h |  7 ++-
 drivers/usb/gadget/function/uvc_video.c | 82 +++++++++++++++++++++++--
 drivers/usb/gadget/legacy/Kconfig       |  1 +
 6 files changed, 107 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 2d152571a7de8..dd58094f0b85b 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -450,6 +450,7 @@ config USB_CONFIGFS_F_UVC
 	depends on USB_CONFIGFS
 	depends on VIDEO_V4L2
 	depends on VIDEO_DEV
+	select VIDEOBUF2_DMA_SG
 	select VIDEOBUF2_VMALLOC
 	select USB_F_UVC
 	help
diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 52f894183ecf0..36b78f8b3cd4c 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -75,6 +75,8 @@ struct uvc_request {
 	struct usb_request *req;
 	u8 *req_buffer;
 	struct uvc_video *video;
+	struct sg_table sgt;
+	u8 header[2];
 };
 
 struct uvc_video {
diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index ff0cc08531d2b..f24ad929ecdae 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -17,6 +17,7 @@
 #include <linux/wait.h>
 
 #include <media/v4l2-common.h>
+#include <media/videobuf2-dma-sg.h>
 #include <media/videobuf2-vmalloc.h>
 
 #include "uvc.h"
@@ -51,6 +52,7 @@ static int uvc_queue_setup(struct vb2_queue *vq,
 	*nplanes = 1;
 
 	sizes[0] = video->imagesize;
+	alloc_devs[0] = video->uvc->v4l2_dev.dev->parent;
 
 	if (cdev->gadget->speed < USB_SPEED_SUPER)
 		video->uvc_num_requests = 4;
@@ -76,7 +78,12 @@ static int uvc_buffer_prepare(struct vb2_buffer *vb)
 		return -ENODEV;
 
 	buf->state = UVC_BUF_STATE_QUEUED;
-	buf->mem = vb2_plane_vaddr(vb, 0);
+	if (queue->use_sg) {
+		buf->sgt = vb2_dma_sg_plane_desc(vb, 0);
+		buf->sg = buf->sgt->sgl;
+	} else {
+		buf->mem = vb2_plane_vaddr(vb, 0);
+	}
 	buf->length = vb2_plane_size(vb, 0);
 	if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
 		buf->bytesused = 0;
@@ -116,9 +123,11 @@ static const struct vb2_ops uvc_queue_qops = {
 	.wait_finish = vb2_ops_wait_finish,
 };
 
-int uvcg_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type,
+int uvcg_queue_init(struct uvc_video_queue *queue, struct device *dev, enum v4l2_buf_type type,
 		    struct mutex *lock)
 {
+	struct uvc_video *video = container_of(queue, struct uvc_video, queue);
+	struct usb_composite_dev *cdev = video->uvc->func.config->cdev;
 	int ret;
 
 	queue->queue.type = type;
@@ -127,9 +136,16 @@ int uvcg_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type,
 	queue->queue.buf_struct_size = sizeof(struct uvc_buffer);
 	queue->queue.ops = &uvc_queue_qops;
 	queue->queue.lock = lock;
-	queue->queue.mem_ops = &vb2_vmalloc_memops;
+	if (cdev->gadget->sg_supported) {
+		queue->queue.mem_ops = &vb2_dma_sg_memops;
+		queue->use_sg = 1;
+	} else {
+		queue->queue.mem_ops = &vb2_vmalloc_memops;
+	}
+
 	queue->queue.timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC
 				     | V4L2_BUF_FLAG_TSTAMP_SRC_EOF;
+	queue->queue.dev = dev;
 	ret = vb2_queue_init(&queue->queue);
 	if (ret)
 		return ret;
diff --git a/drivers/usb/gadget/function/uvc_queue.h b/drivers/usb/gadget/function/uvc_queue.h
index 2f0fff7698430..492492e35bdeb 100644
--- a/drivers/usb/gadget/function/uvc_queue.h
+++ b/drivers/usb/gadget/function/uvc_queue.h
@@ -34,6 +34,9 @@ struct uvc_buffer {
 
 	enum uvc_buffer_state state;
 	void *mem;
+	struct sg_table *sgt;
+	struct scatterlist *sg;
+	unsigned int offset;
 	unsigned int length;
 	unsigned int bytesused;
 };
@@ -50,6 +53,8 @@ struct uvc_video_queue {
 
 	unsigned int buf_used;
 
+	bool use_sg;
+
 	spinlock_t irqlock;	/* Protects flags and irqqueue */
 	struct list_head irqqueue;
 };
@@ -59,7 +64,7 @@ static inline int uvc_queue_streaming(struct uvc_video_queue *queue)
 	return vb2_is_streaming(&queue->queue);
 }
 
-int uvcg_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type,
+int uvcg_queue_init(struct uvc_video_queue *queue, struct device *d, enum v4l2_buf_type type,
 		    struct mutex *lock);
 
 void uvcg_free_buffers(struct uvc_video_queue *queue);
diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 303cb427f687e..9910c2dc6168f 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -23,14 +23,16 @@
  * Video codecs
  */
 
+#define UVCG_REQUEST_HEADER_LEN		2
+
 static int
 uvc_video_encode_header(struct uvc_video *video, struct uvc_buffer *buf,
 		u8 *data, int len)
 {
-	data[0] = 2;
+	data[0] = UVCG_REQUEST_HEADER_LEN;
 	data[1] = UVC_STREAM_EOH | video->fid;
 
-	if (buf->bytesused - video->queue.buf_used <= len - 2)
+	if (buf->bytesused - video->queue.buf_used <= len - UVCG_REQUEST_HEADER_LEN)
 		data[1] |= UVC_STREAM_EOF;
 
 	return 2;
@@ -94,6 +96,71 @@ uvc_video_encode_bulk(struct usb_request *req, struct uvc_video *video,
 		video->payload_size = 0;
 }
 
+static void
+uvc_video_encode_isoc_sg(struct usb_request *req, struct uvc_video *video,
+		struct uvc_buffer *buf)
+{
+	unsigned int pending = buf->bytesused - video->queue.buf_used;
+	struct uvc_request *ureq = req->context;
+	struct scatterlist *sg, *iter;
+	unsigned int len = video->req_size;
+	unsigned int sg_left, part = 0;
+	unsigned int i;
+	int ret;
+
+	sg = ureq->sgt.sgl;
+	sg_init_table(sg, ureq->sgt.nents);
+
+	/* Init the header. */
+	ret = uvc_video_encode_header(video, buf, ureq->header,
+				      video->req_size);
+	sg_set_buf(sg, ureq->header, UVCG_REQUEST_HEADER_LEN);
+	len -= ret;
+
+	if (pending <= len)
+		len = pending;
+
+	req->length = (len == pending) ?
+		len + UVCG_REQUEST_HEADER_LEN : video->req_size;
+
+	/* Init the pending sgs with payload */
+	sg = sg_next(sg);
+
+	for_each_sg(sg, iter, ureq->sgt.nents - 1, i) {
+		if (!len || !buf->sg)
+			break;
+
+		sg_left = sg_dma_len(buf->sg) - buf->offset;
+		part = min_t(unsigned int, len, sg_left);
+
+		sg_set_page(iter, sg_page(buf->sg), part, buf->offset);
+
+		if (part == sg_left) {
+			buf->offset = 0;
+			buf->sg = sg_next(buf->sg);
+		} else {
+			buf->offset += part;
+		}
+		len -= part;
+	}
+
+	/* Assign the video data with header. */
+	req->buf = NULL;
+	req->sg	= ureq->sgt.sgl;
+	req->num_sgs = i + 1;
+
+	req->length -= len;
+	video->queue.buf_used += req->length - UVCG_REQUEST_HEADER_LEN;
+
+	if (buf->bytesused == video->queue.buf_used || !buf->sg) {
+		video->queue.buf_used = 0;
+		buf->state = UVC_BUF_STATE_DONE;
+		buf->offset = 0;
+		uvcg_queue_next_buffer(&video->queue, buf);
+		video->fid ^= UVC_STREAM_FID;
+	}
+}
+
 static void
 uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
 		struct uvc_buffer *buf)
@@ -180,6 +247,8 @@ uvc_video_free_requests(struct uvc_video *video)
 
 	if (video->ureq) {
 		for (i = 0; i < video->uvc_num_requests; ++i) {
+			sg_free_table(&video->ureq[i].sgt);
+
 			if (video->ureq[i].req) {
 				usb_ep_free_request(video->ep, video->ureq[i].req);
 				video->ureq[i].req = NULL;
@@ -233,6 +302,10 @@ uvc_video_alloc_requests(struct uvc_video *video)
 		video->ureq[i].video = video;
 
 		list_add_tail(&video->ureq[i].req->list, &video->req_free);
+		/* req_size/PAGE_SIZE + 1 for overruns and + 1 for header */
+		sg_alloc_table(&video->ureq[i].sgt,
+			       DIV_ROUND_UP(req_size - 2, PAGE_SIZE) + 2,
+			       GFP_KERNEL);
 	}
 
 	video->req_size = req_size;
@@ -342,7 +415,8 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
 		video->encode = uvc_video_encode_bulk;
 		video->payload_size = 0;
 	} else
-		video->encode = uvc_video_encode_isoc;
+		video->encode = video->queue.use_sg ?
+			uvc_video_encode_isoc_sg : uvc_video_encode_isoc;
 
 	schedule_work(&video->pump);
 
@@ -366,7 +440,7 @@ int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
 	video->imagesize = 320 * 240 * 2;
 
 	/* Initialize the video buffers queue. */
-	uvcg_queue_init(&video->queue, V4L2_BUF_TYPE_VIDEO_OUTPUT,
+	uvcg_queue_init(&video->queue, uvc->v4l2_dev.dev, V4L2_BUF_TYPE_VIDEO_OUTPUT,
 			&video->mutex);
 	return 0;
 }
diff --git a/drivers/usb/gadget/legacy/Kconfig b/drivers/usb/gadget/legacy/Kconfig
index 11dd6e8adc8a7..de6668e584815 100644
--- a/drivers/usb/gadget/legacy/Kconfig
+++ b/drivers/usb/gadget/legacy/Kconfig
@@ -502,6 +502,7 @@ config USB_G_WEBCAM
 	tristate "USB Webcam Gadget"
 	depends on VIDEO_V4L2
 	select USB_LIBCOMPOSITE
+	select VIDEOBUF2_DMA_SG
 	select VIDEOBUF2_VMALLOC
 	select USB_F_UVC
 	help
-- 
2.30.2

[PATCH v2 5/5] usb: gadget: uvc: decrease the interrupt load to a quarter

[Michael Grzeschik]

With usb3 we handle many more requests. Decrease the interrupt load by
only enabling the interrupt every quarter of the allocated requests.

Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

--
v1 -> v2:
    - edited patch description
    - removed extra parantheses
    - added a comment for the logic
    - using unsigned int instead of int
    - reinitializing req_int_count in uvcg_video_enable

---
 drivers/usb/gadget/function/uvc.h       |  2 ++
 drivers/usb/gadget/function/uvc_video.c | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 36b78f8b3cd4c..255a61bd6a6a8 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -101,6 +101,8 @@ struct uvc_video {
 	struct list_head req_free;
 	spinlock_t req_lock;
 
+	unsigned int req_int_count;
+
 	void (*encode) (struct usb_request *req, struct uvc_video *video,
 			struct uvc_buffer *buf);
 
diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index 9910c2dc6168f..a1eec38280425 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -362,6 +362,19 @@ static void uvcg_video_pump(struct work_struct *work)
 
 		video->encode(req, video, buf);
 
+		/* With usb3 we have more requests. This will decrease the
+		 * interrupt load to a quarter but also catches the corner
+		 * cases, which needs to be handled */
+		if (list_empty(&video->req_free) ||
+		    buf->state == UVC_BUF_STATE_DONE ||
+		    !(video->req_int_count %
+		       DIV_ROUND_UP(video->uvc_num_requests, 4))) {
+			video->req_int_count = 0;
+			req->no_interrupt = 0;
+		} else {
+			req->no_interrupt = 1;
+		}
+
 		/* Queue the USB request */
 		ret = uvcg_video_ep_queue(video, req);
 		spin_unlock_irqrestore(&queue->irqlock, flags);
@@ -370,6 +383,7 @@ static void uvcg_video_pump(struct work_struct *work)
 			uvcg_queue_cancel(queue, 0);
 			break;
 		}
+		video->req_int_count++;
 	}
 
 	spin_lock_irqsave(&video->req_lock, flags);
@@ -418,6 +432,8 @@ int uvcg_video_enable(struct uvc_video *video, int enable)
 		video->encode = video->queue.use_sg ?
 			uvc_video_encode_isoc_sg : uvc_video_encode_isoc;
 
+	video->req_int_count = 0;
+
 	schedule_work(&video->pump);
 
 	return ret;
-- 
2.30.2

Re: [PATCH v2 0/5] usb: gadget: uvc: improve uvc gadget performance

[Michael Grzeschik]

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Forget about this series. I just missed to point the queue->dev to
the right device in here. Will send v3 later today.

On Mon, Jun 28, 2021 at 10:15:55AM +0200, Michael Grzeschik wrote:
>This series improves the performance of the uvc video gadget by adding a
>zero copy routine using the scatter list interface of the gadget. The
>series also increases the amount of allocated requests depending of the
>speed and it also reduces the interrupt load by only trigger on every
>16th request in case of super-speed.
>
>Michael Grzeschik (5):
>  usb: dwc3: gadget: set gadgets parent to the right controller
>  usb: gadget: uvc: make uvc_num_requests depend on gadget speed
>  usb: gadget: uvc: set v4l2_dev->dev in f_uvc
>  usb: gadget: uvc: add scatter gather support
>  usb: gadget: uvc: decrease the interrupt load to a quarter
>
> drivers/usb/dwc3/gadget.c               |   2 +-
> drivers/usb/gadget/Kconfig              |   1 +
> drivers/usb/gadget/function/f_uvc.c     |   1 +
> drivers/usb/gadget/function/uvc.h       |  15 ++-
> drivers/usb/gadget/function/uvc_queue.c |  28 ++++-
> drivers/usb/gadget/function/uvc_queue.h |   7 +-
> drivers/usb/gadget/function/uvc_video.c | 155 +++++++++++++++++++-----
> drivers/usb/gadget/legacy/Kconfig       |   1 +
> 8 files changed, 175 insertions(+), 35 deletions(-)
>
>-- 
>2.30.2
>
>
>

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