From 326b0e613bc858434198120a17d34308f82c27a8 Mon Sep 17 00:00:00 2001 From: Bhupesh Sharma Date: Fri, 1 Mar 2013 20:46:31 +0100 Subject: [PATCH] usb: gadget: uvc: Make video streaming buffer size comply with USB3.0 SS As per the USB3.0 specs, the bandwidth requirements of a UVC's video streaming endpoint will change to support super-speed. These changes will be dependent on whether the UVC video streaming endpoint is Bulk or Isochronous: - If video streaming endpoint is Isochronous: As per Section 4.4.8.2 (Isochronous Transfer Bandwidth Requirements) of the USB3.0 specs: A SuperSpeed isochronous endpoint can move up to three burst transactions of up to 16 maximum sized packets (3 * 16 * 1024 bytes) per service interval. - If video streaming endpoint is Bulk: As per 4.4.6.1 (Bulk Transfer Data Packet Size) of the USB3.0 specs: An endpoint for bulk transfers shall set the maximum data packet payload size in its endpoint descriptor to 1024 bytes. It also specifies the burst size that the endpoint can accept from or transmit on the SuperSpeed bus. The allowable burst size for a bulk endpoint shall be in the range of 1 to 16. So, in the Isochronous case, we can define the USB request's buffer to be equal to = (Maximum packet size) * (bMaxBurst + 1) * (Mult + 1), so that the UDC driver can try to send out this buffer in one Isochronous service interval. The same computation will hold good for the Bulk case as the Mult value is 0 here and we can have a USB request buffer of maximum 16 * 1024 bytes size, which can be sent out by the UDC driver as per the Bulk bandwidth allocation on the USB3 bus. This patch adds the above-mentioned support and is also USB2.0 backward compliant. Signed-off-by: Bhupesh Sharma Signed-off-by: Laurent Pinchart Tested-by: Bhupesh Sharma Signed-off-by: Felipe Balbi --- drivers/usb/gadget/uvc_video.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/usb/gadget/uvc_video.c b/drivers/usb/gadget/uvc_video.c index 885c393..fac99a9 100644 --- a/drivers/usb/gadget/uvc_video.c +++ b/drivers/usb/gadget/uvc_video.c @@ -229,13 +229,18 @@ uvc_video_free_requests(struct uvc_video *video) static int uvc_video_alloc_requests(struct uvc_video *video) { + unsigned int req_size; unsigned int i; int ret = -ENOMEM; BUG_ON(video->req_size); + req_size = video->ep->maxpacket + * max_t(unsigned int, video->ep->maxburst, 1) + * (video->ep->mult + 1); + for (i = 0; i < UVC_NUM_REQUESTS; ++i) { - video->req_buffer[i] = kmalloc(video->ep->maxpacket, GFP_KERNEL); + video->req_buffer[i] = kmalloc(req_size, GFP_KERNEL); if (video->req_buffer[i] == NULL) goto error; @@ -251,7 +256,8 @@ uvc_video_alloc_requests(struct uvc_video *video) list_add_tail(&video->req[i]->list, &video->req_free); } - video->req_size = video->ep->maxpacket; + video->req_size = req_size; + return 0; error: -- 2.7.4