[PATCH] drm/atomic-helper: Skip vblank waits for unchanged fbs

[Jasper St. Pierre]

With the oops fix:

Reviewed-by: Jasper St. Pierre <jstpierre at mecheye.net>
Tested-by: Jasper St. Pierre <jstpierre at mecheye.net>

On Mon, Nov 24, 2014 at 12:42 PM, Daniel Vetter <daniel.vetter at ffwll.ch>
wrote:

> Especially with legacy cursor ioctls existing userspace assumes that
> you can pile up lots of updates in one go. The super-proper way to
> support this would be a special commit mode which overwrites the last
> update. But getting there will be quite a bit of work.
>
> Meanwhile do what pretty much all the drivers have done for the plane
> update functions: Simply skip the vblank wait for the buffer cleanup
> if the buffer is the same. Since the universal cursor plane code will
> not recreate framebuffers needlessly this allows us to not slow down
> legacy pageflip events while someone moves the cursor around.
>
> v2: Drop the async plane update hunk from a previous attempt at this
> issue.
>
> v3: Fix up kerneldoc.
>
> v4: Don't oops so badly. Reported by Jasper.
>
> Cc: Rob Clark <robdclark at gmail.com>
> Cc: "Jasper St. Pierre" <jstpierre at mecheye.net>
> Reviewed-by: Rob Clark <robdclark at gmail.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 34
> +++++++++++++++++++++++++++++++++-
>  1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c
> b/drivers/gpu/drm/drm_atomic_helper.c
> index af37f1edd3ed..0d32039d072f 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -748,6 +748,33 @@ static void wait_for_fences(struct drm_device *dev,
>         }
>  }
>
> +static bool framebuffer_changed(struct drm_device *dev,
> +                               struct drm_atomic_state *old_state,
> +                               struct drm_crtc *crtc)
> +{
> +       struct drm_plane *plane;
> +       struct drm_plane_state *old_plane_state;
> +       int nplanes = old_state->dev->mode_config.num_total_plane;
> +       int i;
> +
> +       for (i = 0; i < nplanes; i++) {
> +               plane = old_state->planes[i];
> +               old_plane_state = old_state->plane_states[i];
> +
> +               if (!plane)
> +                       continue;
> +
> +               if (plane->state->crtc != crtc &&
> +                   old_plane_state->crtc != crtc)
> +                       continue;
> +
> +               if (plane->state->fb != old_plane_state->fb)
> +                       return true;
> +       }
> +
> +       return false;
> +}
> +
>  /**
>   * drm_atomic_helper_wait_for_vblanks - wait for vblank on crtcs
>   * @dev: DRM device
> @@ -755,7 +782,9 @@ static void wait_for_fences(struct drm_device *dev,
>   *
>   * Helper to, after atomic commit, wait for vblanks on all effected
>   * crtcs (ie. before cleaning up old framebuffers using
> - * drm_atomic_helper_cleanup_planes())
> + * drm_atomic_helper_cleanup_planes()). It will only wait on crtcs where
> the
> + * framebuffers have actually changed to optimize for the legacy cursor
> and
> + * plane update use-case.
>   */
>  void
>  drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
> @@ -781,6 +810,9 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device
> *dev,
>                 if (!crtc->state->enable)
>                         continue;
>
> +               if (!framebuffer_changed(dev, old_state, crtc))
> +                       continue;
> +
>                 ret = drm_crtc_vblank_get(crtc);
>                 if (ret != 0)
>                         continue;
> --
> 2.1.1
>
>


-- 
  Jasper
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