On Wed, May 19, 2021 at 11:38:53AM -0700, Rob Clark wrote:
From: Rob Clark robdclark@chromium.org
Signed-off-by: Rob Clark robdclark@chromium.org
drivers/gpu/drm/drm_atomic_helper.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index 560aaecba31b..fe10fc2e7f86 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -1435,11 +1435,15 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev, int i, ret;
for_each_new_plane_in_state(state, plane, new_plane_state, i) {
u64 vblank_count;if (!new_plane_state->fence) continue;
WARN_ON(!new_plane_state->fb);
vblank_count = drm_crtc_vblank_count(new_plane_state->crtc);/*
- If waiting for fences pre-swap (ie: nonblock), userspace can
- still interrupt the operation. Instead of blocking until the
@@ -1449,6 +1453,13 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev, if (ret) return ret;
/** Check if we've missed a vblank while waiting, and if we have* signal the fence that it's signaler should be boosted*/if (vblank_count != drm_crtc_vblank_count(new_plane_state->crtc))dma_fence_boost(new_plane_state->fence);
I think we should do a lot better here: - maybe only bother doing this for single-crtc updates, and only if modeset isn't set. No one else cares about latency.
- We should boost _right_ when we've missed the frame, so I think we should have a _timeout wait here that guesstimates when the vblank is over (might need to throw in a vblank wait if we missed) and then boost immediately. Not wait a bunch of frames (worst case) until we finally decide to boost.
Otherwise I really like this, I think it's about the only real reason i915 isn't using atomic helpers.
Also adding Matt B for this topic. -Daniel
- dma_fence_put(new_plane_state->fence); new_plane_state->fence = NULL; }
-- 2.30.2