On 2023-02-18 16:15, Rob Clark wrote:
> From: Rob Clark <robdcl...@chromium.org>
>
> For an atomic commit updating a single CRTC (ie. a pageflip) calculate
> the next vblank time, and inform the fence(s) of that deadline.
>
> v2: Comment typo fix (danvet)
>
> Signed-off-by: Rob Clark <robdcl...@chromium.org>
> Reviewed-by: Daniel Vetter <daniel.vet...@ffwll.ch>
> Signed-off-by: Rob Clark <robdcl...@chromium.org>
> ---
> drivers/gpu/drm/drm_atomic_helper.c | 36 +++++++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c
> b/drivers/gpu/drm/drm_atomic_helper.c
> index d579fd8f7cb8..35a4dc714920 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1511,6 +1511,40 @@ void drm_atomic_helper_commit_modeset_enables(struct
> drm_device *dev,
> }
> EXPORT_SYMBOL(drm_atomic_helper_commit_modeset_enables);
>
> +/*
> + * For atomic updates which touch just a single CRTC, calculate the time of
> the
> + * next vblank, and inform all the fences of the deadline.
> + */
> +static void set_fence_deadline(struct drm_device *dev,
> + struct drm_atomic_state *state)
> +{
> + struct drm_crtc *crtc, *wait_crtc = NULL;
> + struct drm_crtc_state *new_crtc_state;
> + struct drm_plane *plane;
> + struct drm_plane_state *new_plane_state;
> + ktime_t vbltime;
I've not looked at the latest language spec, but is AFAIR "vbltime"
would be uninitialized here. Has this changed?
> + int i;
> +
> + for_each_new_crtc_in_state (state, crtc, new_crtc_state, i) {
> + if (wait_crtc)
> + return;
> + wait_crtc = crtc;
> + }
> +
> + /* If no CRTCs updated, then nothing to do: */
> + if (!wait_crtc)
> + return;
> +
> + if (drm_crtc_next_vblank_time(wait_crtc, &vbltime))
> + return;
We have a problem here in that we're adding the time remaining to the next
vblank event to an uninitialized local variable. As per my comment on patch 10,
I'd rather drm_crtc_next_vblank_time() yield the time remaining to the vblank
event,
and we can do the arithmetic locally here in this function.
--
Regards,
Luben
> +
> + for_each_new_plane_in_state (state, plane, new_plane_state, i) {
> + if (!new_plane_state->fence)
> + continue;
> + dma_fence_set_deadline(new_plane_state->fence, vbltime);
> + }
> +}
> +
> /**
> * drm_atomic_helper_wait_for_fences - wait for fences stashed in plane state
> * @dev: DRM device
> @@ -1540,6 +1574,8 @@ int drm_atomic_helper_wait_for_fences(struct drm_device
> *dev,
> struct drm_plane_state *new_plane_state;
> int i, ret;
>
> + set_fence_deadline(dev, state);
> +
> for_each_new_plane_in_state(state, plane, new_plane_state, i) {
> if (!new_plane_state->fence)
> continue;
