On Wed, Jan 13, 2016 at 12:53:34PM +0000, John Keeping wrote:
> As commented in drm_atomic_helper_wait_for_vblanks(), userspace relies
> on cursor ioctls being unsynced. Converting the rockchip driver to
> atomic has significantly impacted cursor performance by making every
> cursor update wait for vblank.
>
> By skipping the vblank sync when the framebuffer has not changed (as is
> done in drm_atomic_helper_wait_for_vblanks()) we can avoid this for the
> common case of moving the cursor and only need to delay the cursor ioctl
> when the cursor icon changes.
>
> I originally inserted a check on legacy_cursor_update as well, but that
> caused a storm of iommu page faults. I didn't investigate the cause of
> those since this change gives enough of a performance improvement for my
> use case.
>
> This is RFC because of that and because the framebuffer_changed()
> function is copied from drm_atomic_helper.c as a quick way to test the
> result.
>
> Signed-off-by: John Keeping <john at metanate.com>
> ---
> drivers/gpu/drm/rockchip/rockchip_drm_fb.c | 27 +++++++++++++++++++++++++--
> 1 file changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> index f784488..8fd9821 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
> @@ -177,8 +177,28 @@ static void rockchip_crtc_wait_for_update(struct
> drm_crtc *crtc)
> crtc_funcs->wait_for_update(crtc);
> }
>
> +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 i;
> +
> + for_each_plane_in_state(old_state, plane, old_plane_state, i) {
> + if (plane->state->crtc != crtc &&
> + old_plane_state->crtc != crtc)
> + continue;
> +
> + if (plane->state->fb != old_plane_state->fb)
> + return true;
> + }
> +
> + return false;
> +}
Please don't hand-roll logic that affects semantics like this. Instead
please use drm_atomic_helper_wait_for_vblanks(), which should do this
correctly for you.
If that's not the case then we need to improve the generic helper, or
figure out what's different with rockhip.
Thanks, Daniel
> +
> static void
> -rockchip_atomic_wait_for_complete(struct drm_atomic_state *old_state)
> +rockchip_atomic_wait_for_complete(struct drm_device *dev, struct
> drm_atomic_state *old_state)
> {
> struct drm_crtc_state *old_crtc_state;
> struct drm_crtc *crtc;
> @@ -194,6 +214,9 @@ rockchip_atomic_wait_for_complete(struct drm_atomic_state
> *old_state)
> if (!crtc->state->active)
> continue;
>
> + if (!framebuffer_changed(dev, old_state, crtc))
> + continue;
> +
> ret = drm_crtc_vblank_get(crtc);
> if (ret != 0)
> continue;
> @@ -241,7 +264,7 @@ rockchip_atomic_commit_complete(struct
> rockchip_atomic_commit *commit)
>
> drm_atomic_helper_commit_planes(dev, state, true);
>
> - rockchip_atomic_wait_for_complete(state);
> + rockchip_atomic_wait_for_complete(dev, state);
>
> drm_atomic_helper_cleanup_planes(dev, state);
>
> --
> 2.7.0.rc3.140.g520a093
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
