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FROMGIT: usb: gadget: uvc: calculate the number of request depending on framesize

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The current limitation of possible number of requests being handled is
dependent on the gadget speed. It makes more sense to depend on the
typical frame size when calculating the number of requests. This patch
is changing this and is using the previous limits as boundaries for
reasonable minimum and maximum number of requests.

For a 1080p jpeg encoded video stream with a maximum imagesize of
e.g. 800kB with a maxburst of 8 and an multiplier of 1 the resulting
number of requests is calculated to 49.

        800768         1
nreqs = ------ * -------------- ~= 49
          2      (1024 * 8 * 1)

Tested-by: Dan Vacura <w36195@motorola.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lore.kernel.org/r/20220529223848.105914-2-m.grzeschik@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Bug: 234757296
(cherry picked from commit 87d76b5f1d8eeb49efa16e2018e188864cbb9401
 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-next)
Change-Id: I0228cbaa56d4e75bed33e1ef721ae3127d779faf
Signed-off-by: Dan Vacura <w36195@motorola.com>
This commit is contained in:
Michael Grzeschik 2022-05-30 00:38:46 +02:00 committed by Dan Vacura
parent 59d057a3f9
commit b92ac32536
1 changed files with 12 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
drivers/usb/gadget/function/uvc_queue.c
View File

@ -43,7 +43,8 @@ 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;
unsigned int req_size;
unsigned int nreq;
if (*nbuffers > UVC_MAX_VIDEO_BUFFERS)
*nbuffers = UVC_MAX_VIDEO_BUFFERS;
@ -52,10 +53,16 @@ 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;
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);
video->uvc_num_requests = nreq;
return 0;
}