[RFC 0/4] dma-fence: Deadline awareness

Rob Clark robdclark at gmail.com
Mon Jul 26 23:38:47 UTC 2021

From: Rob Clark <robdclark at chromium.org>

Based on discussion from a previous series[1] to add a "boost" mechanism
when, for example, vblank deadlines are missed.  Instead of a boost
callback, this approach adds a way to set a deadline on the fence, by
which the waiter would like to see the fence signalled.

I've not yet had a chance to re-work the drm/msm part of this, but
wanted to send this out as an RFC in case I don't have a chance to
finish the drm/msm part this week.

Original description:

In some cases, like double-buffered rendering, missing vblanks can
trick the GPU into running at a lower frequence, when really we
want to be running at a higher frequency to not miss the vblanks
in the first place.

This is partially inspired by a trick i915 does, but implemented
via dma-fence for a couple of reasons:

1) To continue to be able to use the atomic helpers
2) To support cases where display and gpu are different drivers

[1] https://patchwork.freedesktop.org/series/90331/

Rob Clark (4):
  dma-fence: Add deadline awareness
  drm/vblank: Add helper to get next vblank time
  drm/atomic-helper: Set fence deadline for vblank
  drm/scheduler: Add fence deadline support

 drivers/dma-buf/dma-fence.c             | 39 +++++++++++++++++++++++++
 drivers/gpu/drm/drm_atomic_helper.c     | 36 +++++++++++++++++++++++
 drivers/gpu/drm/drm_vblank.c            | 31 ++++++++++++++++++++
 drivers/gpu/drm/scheduler/sched_fence.c | 10 +++++++
 drivers/gpu/drm/scheduler/sched_main.c  |  3 ++
 include/drm/drm_vblank.h                |  1 +
 include/linux/dma-fence.h               | 17 +++++++++++
 7 files changed, 137 insertions(+)


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