| Message ID | 20170307003653.11645-1-daniel.vetter@ffwll.ch (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Daniel, Thank you for the patch. On Tuesday 07 Mar 2017 01:36:53 Daniel Vetter wrote: > Worst case if the hw can't support completion signalling in a > race-free way we want the event to be too late, not too early. > > Text adapted from a proposal from Laurent - the other side of how to > make hw work correctly where it's possible is imo already sufficiently > documented. > > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> > --- > include/drm/drm_crtc.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h > index bda9347554a1..444200017f8c 100644 > --- a/include/drm/drm_crtc.h > +++ b/include/drm/drm_crtc.h > @@ -204,6 +204,13 @@ struct drm_crtc_state { > * drm_crtc_arm_vblank_event(). See the documentation of that function > * for a detailed discussion of the constraints it needs to be used > * safely. > + * > + * If the device can't notify of flip completion in a race-free way in s/ in$// > + * at all, then the event should be armed just after the page flip is > + * committed. In the worst case the driver will send the event to > + * userspace one frame too late. This doesn't allow for a real atomic > + * update, but it should avoid tearing. The R-Car Gen2 hardware falls > + * in this category. I'm not sure would special-case R-Car Gen2 here :-) > */ > struct drm_pending_vblank_event *event;
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h index bda9347554a1..444200017f8c 100644 --- a/include/drm/drm_crtc.h +++ b/include/drm/drm_crtc.h @@ -204,6 +204,13 @@ struct drm_crtc_state { * drm_crtc_arm_vblank_event(). See the documentation of that function * for a detailed discussion of the constraints it needs to be used * safely. + * + * If the device can't notify of flip completion in a race-free way in + * at all, then the event should be armed just after the page flip is + * committed. In the worst case the driver will send the event to + * userspace one frame too late. This doesn't allow for a real atomic + * update, but it should avoid tearing. The R-Car Gen2 hardware falls + * in this category. */ struct drm_pending_vblank_event *event;
Worst case if the hw can't support completion signalling in a race-free way we want the event to be too late, not too early. Text adapted from a proposal from Laurent - the other side of how to make hw work correctly where it's possible is imo already sufficiently documented. Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> --- include/drm/drm_crtc.h | 7 +++++++ 1 file changed, 7 insertions(+)