[PATCH v5 20/21] usb: dwc2: host: Totally redo the microframe scheduler

[Doug Anderson]

Hi,

On Fri, Jan 22, 2016 at 10:18 AM, Douglas Anderson
<dianders at chromium.org> wrote:
> This totally reimplements the microframe scheduler in dwc2 to attempt to
> handle periodic splits properly.  The old code didn't even try, so this
> was a significant effort since periodic splits are one of the most
> complicated things in USB.
>
> I've attempted to keep the old "don't use the microframe" schduler
> around for now, but not sure it's needed.  It has also only been lightly
> tested.
>
> I think it's pretty certain that this scheduler isn't perfect and might
> have some bugs, but it seems much better than what was there before.
> With this change my stressful USB test (USB webcam + USB audio + some
> keyboards) crackles less.
>
> Signed-off-by: Douglas Anderson <dianders at chromium.org>
> ---
> Changes in v5:
> - Moved defines outside of ifdef to avoid gadget-only compile error.
>
> Changes in v4:
> - Figured out what the microframe scheduler was supposed to do.
> - Microframe rewrite is totally different from v3, hopefully more right.
> - Microframe rewrite is later in the series now.
>
> Changes in v3:
> - The uframe scheduler patch is folded into optimization series.
> - Optimize uframe scheduler "single uframe" case a little.
> - uframe scheduler now atop logging patches.
> - uframe scheduler now before delayed bandwidth release patches.
> - Add defines like EARLY_FRAME_USEC
> - Reorder dwc2_deschedule_periodic() in prep for future patches.
> - uframe scheduler now shows real usefulness w/ future patches!
> - Assuming single_tt is new for v3; not terribly well tested (yet).
> - Keep track and use our uframe new for v3.
>
> Changes in v2:
> - Totally rewrote uframe scheduler again after writing test code.
> - uframe scheduler atop delayed bandwidth release patches.
>
>  drivers/usb/dwc2/core.h      |   85 ++-
>  drivers/usb/dwc2/hcd.c       |   87 ++-
>  drivers/usb/dwc2/hcd.h       |   79 ++-
>  drivers/usb/dwc2/hcd_queue.c | 1208 +++++++++++++++++++++++++++++++++++-------
>  4 files changed, 1271 insertions(+), 188 deletions(-)

Needs more testing, but possibly the next version of this patch will
include <https://chromium-review.googlesource.com/#/c/323326/>.  If
you happen to be testing / reviewing this patch, please consider it
with the proposed fixup.  I'm happy to send out a squashed version if
that makes someone's review easier.

-Doug