Re: [RFC/RFT PATCH 0/6] Asynchronous UVC

From: Kieran Bingham
Date: Tue Jun 05 2018 - 05:01:55 EST

Hi Troy

On 03/01/18 21:13, Troy Kisky wrote:
> On 1/3/2018 12:32 PM, Kieran Bingham wrote:
>> From: Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx>
>> 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 or the Logitech Brio 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
>> âmemcpyâ 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.
> I have a rather large patch that does provide frame buffers directly for bulk
> cameras. It cannot be used with ISOC cameras. But it is currently for 4.1.
> I'll be porting it to 4.9 in a few days if you'd like to see it.

How did you get on with this porting activity?

Is it possible to share any of this work with the mailing lists ?

(If you have not ported to v4.9 - I think it would be useful even to post the
v4.1 patch and we can look at what's needed for getting it ported to mainline)



> BR
> Troy
>> Extra throughput is possible by moving the actual memcpy actions to a work
>> queue, and moving the memcpy out of interrupt context and allowing work tasks
>> to be scheduled across multiple cores.
>> This series has been tested on both the ZED and Brio cameras on arm64
>> platforms, however due to the intrinsic changes in the driver I would like to
>> see it tested with other devices and other platforms, so I'd appreciate if
>> anyone can test this on a range of USB cameras.
>> Kieran Bingham (6):
>> uvcvideo: Refactor URB descriptors
>> uvcvideo: Convert decode functions to use new context structure
>> uvcvideo: Protect queue internals with helper
>> uvcvideo: queue: Simplify spin-lock usage
>> uvcvideo: queue: Support asynchronous buffer handling
>> uvcvideo: Move decode processing to process context
>> drivers/media/usb/uvc/uvc_isight.c | 4 +-
>> drivers/media/usb/uvc/uvc_queue.c | 115 ++++++++++++++----
>> drivers/media/usb/uvc/uvc_video.c | 191 ++++++++++++++++++++++--------
>> drivers/media/usb/uvc/uvcvideo.h | 56 +++++++--
>> 4 files changed, 289 insertions(+), 77 deletions(-)
>> base-commit: 6f0e5fd39143a59c22d60e7befc4f33f22aeed2f