usb: gadget: uvc: set req_length based on payload by nreqs instead of req_size

Compressed formats generate content depending amount of data that is set
in the vb2 buffer by the payload_size. When streaming those formats it
is better to scatter that smaller data over all requests. This patch is
doing that by introducing the calculated req_payload_size which is
updated by each frame. It the uses this amount of data to fill the
isoc requests instead of the video->req_size.

For uncompressed formats it will not make a difference since the payload
size will be equal to the imagesize. Therefore the code will have no
effecta as req_payload_size will be equal to req_size.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lore.kernel.org/r/20240403-uvc_request_length_by_interval-v7-6-e224bb1035f0@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 20 insertions, 9 deletions

diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index 099038f1088e..bedb4ef42864 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -110,6 +110,8 @@ struct uvc_video {
 
 	unsigned int uvc_num_requests;
 
+	unsigned int reqs_per_frame;
+
 	/* Requests */
 	bool is_enabled; /* tracks whether video stream is enabled */
 	unsigned int req_size;
diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index 731e3b9d21ac..6757a4e25a74 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -58,6 +58,7 @@ static int uvc_queue_setup(struct vb2_queue *vq,
 static int uvc_buffer_prepare(struct vb2_buffer *vb)
 {
 	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
+	struct uvc_video *video = container_of(queue, struct uvc_video, queue);
 	struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
 	struct uvc_buffer *buf = container_of(vbuf, struct uvc_buffer, buf);
 
@@ -78,10 +79,15 @@ static int uvc_buffer_prepare(struct vb2_buffer *vb)
 		buf->mem = vb2_plane_vaddr(vb, 0);
 	}
 	buf->length = vb2_plane_size(vb, 0);
-	if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
+	if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
 		buf->bytesused = 0;
-	else
+	} else {
 		buf->bytesused = vb2_get_plane_payload(vb, 0);
+		buf->req_payload_size =
+			  DIV_ROUND_UP(buf->bytesused +
+				       (video->reqs_per_frame * UVCG_REQUEST_HEADER_LEN),
+				       video->reqs_per_frame);
+	}
 
 	return 0;
 }
diff --git a/drivers/usb/gadget/function/uvc_queue.h b/drivers/usb/gadget/function/uvc_queue.h
index 41f87b917f6b..b54becc570a3 100644
--- a/drivers/usb/gadget/function/uvc_queue.h
+++ b/drivers/usb/gadget/function/uvc_queue.h
@@ -39,6 +39,8 @@ struct uvc_buffer {
 	unsigned int offset;
 	unsigned int length;
 	unsigned int bytesused;
+	/* req_payload_size: only used with isoc */
+	unsigned int req_payload_size;
 };
 
 #define UVC_QUEUE_DISCONNECTED		(1 << 0)
diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index ecb32a3e0376..677eaf5b7e4d 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -136,7 +136,7 @@ uvc_video_encode_isoc_sg(struct usb_request *req, struct uvc_video *video,
 	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 len = buf->req_payload_size;
 	unsigned int sg_left, part = 0;
 	unsigned int i;
 	int header_len;
@@ -146,15 +146,15 @@ uvc_video_encode_isoc_sg(struct usb_request *req, struct uvc_video *video,
 
 	/* Init the header. */
 	header_len = uvc_video_encode_header(video, buf, ureq->header,
-				      video->req_size);
+					     buf->req_payload_size);
 	sg_set_buf(sg, ureq->header, header_len);
 	len -= header_len;
 
 	if (pending <= len)
 		len = pending;
 
-	req->length = (len == pending) ?
-		len + header_len : video->req_size;
+	req->length = (len == pending) ? len + header_len :
+		buf->req_payload_size;
 
 	/* Init the pending sgs with payload */
 	sg = sg_next(sg);
@@ -202,7 +202,7 @@ uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
 {
 	void *mem = req->buf;
 	struct uvc_request *ureq = req->context;
-	int len = video->req_size;
+	int len = buf->req_payload_size;
 	int ret;
 
 	/* Add the header. */
@@ -214,7 +214,7 @@ uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
 	ret = uvc_video_encode_data(video, buf, mem, len);
 	len -= ret;
 
-	req->length = video->req_size - len;
+	req->length = buf->req_payload_size - len;
 
 	if (buf->bytesused == video->queue.buf_used ||
 			video->queue.flags & UVC_QUEUE_DROP_INCOMPLETE) {
@@ -504,7 +504,7 @@ uvc_video_prep_requests(struct uvc_video *video)
 
 	if (!usb_endpoint_xfer_isoc(video->ep->desc)) {
 		video->req_size = max_req_size;
-		video->uvc_num_requests =
+		video->reqs_per_frame = video->uvc_num_requests =
 			DIV_ROUND_UP(video->imagesize, max_req_size);
 
 		return;
@@ -535,6 +535,7 @@ uvc_video_prep_requests(struct uvc_video *video)
 	 * able to fully encode one frame.
 	 */
 	video->uvc_num_requests = nreq + UVCG_REQ_MAX_ZERO_COUNT;
+	video->reqs_per_frame = nreq;
 }
 
 static int