[PATCH hwc v2 6/6] drm_hwcomposer: Add out-fence support

[Sean Paul]

On Wed, Sep 27, 2017 at 7:58 AM, Robert Foss <robert.foss at collabora.com> wrote:
> Add support for out-fences through the OUT_FENCE_PTR property.
> Out-fences signal when their associated buffer may be read by a device.
>
> Signed-off-by: Robert Foss <robert.foss at collabora.com>
> ---
>
> Changes since v1:
>   Sergi Granell
>     - Set atomic property to be out_fences[crtc->pipe()] not out_fences[0]
>
>  drmdisplaycomposition.h  |  9 +++++++++
>  drmdisplaycompositor.cpp | 16 ++++++++++++++++
>  drmhwctwo.cpp            |  9 ++-------
>  3 files changed, 27 insertions(+), 7 deletions(-)
>
> diff --git a/drmdisplaycomposition.h b/drmdisplaycomposition.h
> index b165adc..0586d58 100644
> --- a/drmdisplaycomposition.h
> +++ b/drmdisplaycomposition.h
> @@ -189,6 +189,14 @@ class DrmDisplayComposition {
>      return planner_;
>    }
>
> +  int take_out_fence() {
> +    return out_fence_.Release();
> +  }
> +
> +  void set_out_fence(int out_fence) {
> +    out_fence_.Set(dup(out_fence));

Why dup if you're just going to close the original? I think the helper
functions actually hurt you here. It would be easier to understand
what was going on if you just manipulated out_fence_ directly in
CommitFrame (then you wouldn't need the dup/close).

> +  }
> +
>    void Dump(std::ostringstream *out) const;
>
>   private:
> @@ -215,6 +223,7 @@ class DrmDisplayComposition {
>    int timeline_current_ = 0;
>    int timeline_squash_done_ = 0;
>    int timeline_pre_comp_done_ = 0;
> +  UniqueFd out_fence_ = -1;
>
>    bool geometry_changed_;
>    std::vector<DrmHwcLayer> layers_;
> diff --git a/drmdisplaycompositor.cpp b/drmdisplaycompositor.cpp
> index 71c0451..a1427d3 100644
> --- a/drmdisplaycompositor.cpp
> +++ b/drmdisplaycompositor.cpp
> @@ -492,6 +492,7 @@ int DrmDisplayCompositor::CommitFrame(DrmDisplayComposition *display_comp,
>        display_comp->composition_planes();
>    std::vector<DrmCompositionRegion> &pre_comp_regions =
>        display_comp->pre_comp_regions();
> +  uint64_t out_fences[drm_->GetCrtcCount()];

Huh. I didn't know you could do this.

>
>    DrmConnector *connector = drm_->GetConnectorForDisplay(display_);
>    if (!connector) {
> @@ -510,6 +511,16 @@ int DrmDisplayCompositor::CommitFrame(DrmDisplayComposition *display_comp,
>      return -ENOMEM;
>    }
>
> +  if (crtc->out_fence_ptr_property().id() != 0) {
> +    ret = drmModeAtomicAddProperty(pset, crtc->id(), crtc->out_fence_ptr_property().id(),
> +                                   (uint64_t) &out_fences[crtc->pipe()]);
> +    if (ret < 0) {
> +      ALOGE("Failed to add OUT_FENCE_PTR property to pset: %d", ret);
> +      drmModeAtomicFree(pset);
> +      return ret;
> +    }
> +  }
> +
>    if (mode_.needs_modeset) {
>      ret = drmModeAtomicAddProperty(pset, crtc->id(), crtc->mode_property().id(),
>                                     mode_.blob_id) < 0 ||
> @@ -708,6 +719,11 @@ out:
>      mode_.needs_modeset = false;
>    }
>
> +  if (crtc->out_fence_ptr_property().id()) {
> +    display_comp->set_out_fence((int) out_fences[crtc->pipe()]);
> +    close((int) out_fences[crtc->pipe()]);
> +  }
> +
>    return ret;
>  }
>
> diff --git a/drmhwctwo.cpp b/drmhwctwo.cpp
> index 762ee8c..89399bf 100644
> --- a/drmhwctwo.cpp
> +++ b/drmhwctwo.cpp
> @@ -557,19 +557,14 @@ HWC2::Error DrmHwcTwo::HwcDisplay::PresentDisplay(int32_t *retire_fence) {
>      i = overlay_planes.erase(i);
>    }
>
> +  AddFenceToRetireFence(composition->take_out_fence());
> +
>    ret = compositor_.ApplyComposition(std::move(composition));
>    if (ret) {
>      ALOGE("Failed to apply the frame composition ret=%d", ret);
>      return HWC2::Error::BadParameter;
>    }
>
> -  // Now that the release fences have been generated by the compositor, make
> -  // sure they're managed properly
> -  for (std::pair<const uint32_t, DrmHwcTwo::HwcLayer *> &l : z_map) {
> -    l.second->manage_release_fence();
> -    AddFenceToRetireFence(l.second->release_fence());
> -  }
> -
>    // The retire fence returned here is for the last frame, so return it and
>    // promote the next retire fence
>    *retire_fence = retire_fence_.Release();
> --
> 2.11.0
>