The Linux UVC driver has long provided adequate performance capabilities for web-cams and low data rate video devices in Linux while resolutions were low.
Modern USB cameras are now capable of high data rates thanks to USB3 with 1080p, and even 4k capture resolutions supported. Cameras such as the Stereolabs ZED (bulk transfers) or the Logitech BRIO (isochronous transfers) can generate more data than an embedded ARM core is able to process on a single core, resulting in frame loss. A large part of this performance impact is from the requirement to ‘memcpy’ frames out from URB packets to destination frames. This unfortunate requirement is due to the UVC protocol allowing a variable length header, and thus it is not possible to provide the target frame buffers directly. Extra throughput is possible by moving the actual memcpy actions to a work queue, and moving the memcpy out of interrupt context thus allowing work tasks to be scheduled across multiple cores. This series has been tested on both the ZED and BRIO cameras on arm64 platforms, and with thanks to Randy Dunlap, a Dynex 1.3MP Webcam, a Sonix USB2 Camera, and a built in Toshiba Laptop camera, and with thanks to Philipp Zabel for testing on a Lite-On internal Laptop Webcam, Logitech C910 (USB2 isoc), Oculus Sensor (USB3 isoc), and Microsoft HoloLens Sensors (USB3 bulk). As far as I am aware iSight devices, and devices which use UVC to encode data (output device) have not yet been tested - but should find no ill effect (at least not until they are tested of course :D ) Tested-by: Randy Dunlap <rdun...@infradead.org> Tested-by: Philipp Zabel <philipp.za...@gmail.com> v2: - Fix race reported by Guennadi v3: - Fix similar race reported by Laurent - Only queue work if required (encode/isight do not queue work) - Refactor/Rename variables for clarity v4: - (Yet another) Rework of the uninitialise path. This time to hopefully clean up the shutdown races for good. use usb_poison_urb() to halt all URBs, then flush the work queue before freeing. - Rebase to latest linux-media/master Kieran Bingham (6): media: uvcvideo: Refactor URB descriptors media: uvcvideo: Convert decode functions to use new context structure media: uvcvideo: Protect queue internals with helper media: uvcvideo: queue: Simplify spin-lock usage media: uvcvideo: queue: Support asynchronous buffer handling media: uvcvideo: Move decode processing to process context drivers/media/usb/uvc/uvc_isight.c | 6 +- drivers/media/usb/uvc/uvc_queue.c | 102 +++++++++++++---- drivers/media/usb/uvc/uvc_video.c | 180 +++++++++++++++++++++--------- drivers/media/usb/uvc/uvcvideo.h | 59 ++++++++-- 4 files changed, 266 insertions(+), 81 deletions(-) base-commit: a77cfdf6bd06eef0dadea2b541a7c01502b1b4f6 -- git-series 0.9.1