linux-kernel - [PATCH v4 08/10] usb: gadget: uvc: set req_size and n

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Message-Id: <20240403-uvc_request_length_by_interval-v4-8-ca22f334226e@pengutronix.de>
Date: Tue, 13 Aug 2024 11:09:32 +0200
From: Michael Grzeschik <m.grzeschik@...gutronix.de>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Daniel Scally <dan.scally@...asonboard.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Avichal Rakesh <arakesh@...gle.com>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Michael Grzeschik <m.grzeschik@...gutronix.de>
Subject: [PATCH v4 08/10] usb: gadget: uvc: set req_size and n_requests
 based on the frame interval

With the information of the interval frame length it is now possible to
calculate the number of usb requests by the frame duration. Based on the
request size and the imagesize we calculate the actual size per request.
This calculation has the benefit that the frame data is equally
distributed over all allocated requests.

We keep the current req_size calculation as a fallback, if the interval
callbacks did not set the interval property.

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

---
v3 -> v4: -
v2 -> v3:
 - added the frame duration for full-speed devices into calculation
v1 -> v2:
 - add headersize per request into calculation
---
 drivers/usb/gadget/function/uvc_queue.c | 35 ++++++++++++++++++++++++++-------
 drivers/usb/gadget/function/uvc_video.c |  2 +-
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index 2414d78b031f4..ab04df0e4f360 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -44,7 +44,9 @@ 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);
-	unsigned int req_size;
+	struct usb_composite_dev *cdev = video->uvc->func.config->cdev;
+	unsigned int interval_duration = video->ep->desc->bInterval * 1250;
+	unsigned int req_size, max_req_size, header_size;
 	unsigned int nreq;
 
 	if (*nbuffers > UVC_MAX_VIDEO_BUFFERS)
@@ -54,15 +56,34 @@ static int uvc_queue_setup(struct vb2_queue *vq,
 
 	sizes[0] = video->imagesize;
 
-	req_size = video->ep->maxpacket
+	if (cdev->gadget->speed < USB_SPEED_HIGH)
+		interval_duration = video->ep->desc->bInterval * 10000;
+
+	nreq = DIV_ROUND_UP(video->interval, interval_duration);
+
+	header_size = nreq * UVCG_REQUEST_HEADER_LEN;
+
+	req_size = DIV_ROUND_UP(video->imagesize + header_size, nreq);
+
+	max_req_size = video->ep->maxpacket
 		 * max_t(unsigned int, video->ep->maxburst, 1)
 		 * (video->ep->mult);
 
-	/* We divide by two, to increase the chance to run
-	 * into fewer requests for smaller framesizes.
-	 */
-	nreq = DIV_ROUND_UP(DIV_ROUND_UP(sizes[0], 2), req_size);
-	nreq = clamp(nreq, 4U, 64U);
+	if (!req_size) {
+		req_size = max_req_size;
+
+		/* We divide by two, to increase the chance to run
+		 * into fewer requests for smaller framesizes.
+		 */
+		nreq = DIV_ROUND_UP(DIV_ROUND_UP(sizes[0], 2), req_size);
+		nreq = clamp(nreq, 4U, 64U);
+	} else if (req_size > max_req_size) {
+		/* The prepared interval length and expected buffer size
+		 * is not possible to stream with the currently configured
+		 * isoc bandwidth
+		 */
+		return -EINVAL;
+	}
 
 	video->req_size = req_size;
 	video->uvc_num_requests = nreq;
diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index a6786beef91ad..fe19608b57720 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -307,7 +307,7 @@ static int uvcg_video_usb_req_queue(struct uvc_video *video,
 		if (list_empty(&video->req_free) || ureq->last_buf ||
 				!req->length ||
 			!(video->req_int_count %
-			DIV_ROUND_UP(video->uvc_num_requests, 4))) {
+			clamp(DIV_ROUND_UP(video->uvc_num_requests, 4), 4U, 16U))) {
 			video->req_int_count = 0;
 			req->no_interrupt = 0;
 		} else {

-- 
2.39.2