Re: [PATCH v2 0/5] dma-fence: Deadline awareness

[Christian König]

The general approach seems to make sense now I think.

One minor thing which I'm missing is adding support for this to the 
dma_fence_array and dma_fence_chain containers.

Regards,
Christian.

Am 07.08.21 um 20:37 schrieb Rob Clark:
> From: Rob Clark <robdclark@xxxxxxxxxxxx>
>
> 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/
>
> v1: https://patchwork.freedesktop.org/series/93035/
> v2: Move filtering out of later deadlines to fence implementation
>      to avoid increasing the size of dma_fence
>
> Rob Clark (5):
>    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
>    drm/msm: Add deadline based boost support
>
>   drivers/dma-buf/dma-fence.c             | 20 +++++++
>   drivers/gpu/drm/drm_atomic_helper.c     | 36 ++++++++++++
>   drivers/gpu/drm/drm_vblank.c            | 31 ++++++++++
>   drivers/gpu/drm/msm/msm_fence.c         | 76 +++++++++++++++++++++++++
>   drivers/gpu/drm/msm/msm_fence.h         | 20 +++++++
>   drivers/gpu/drm/msm/msm_gpu.h           |  1 +
>   drivers/gpu/drm/msm/msm_gpu_devfreq.c   | 20 +++++++
>   drivers/gpu/drm/scheduler/sched_fence.c | 25 ++++++++
>   drivers/gpu/drm/scheduler/sched_main.c  |  3 +
>   include/drm/drm_vblank.h                |  1 +
>   include/drm/gpu_scheduler.h             |  6 ++
>   include/linux/dma-fence.h               | 16 ++++++
>   12 files changed, 255 insertions(+)