On Sun, Nov 02, 2014 at 02:19:26PM +0100, Daniel Vetter wrote: > No helper function to do it all yet provided since no driver has > support for driver core fences yet. Which we'd need to make the > implementation really generic. > > v2: Clarify async howto a bit per the discussion With Rob Clark. > > Cc: Rob Clark <robdclark@xxxxxxxxx> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Reviewed-by: Sean Paul <seanpaul@xxxxxxxxxxxx> > --- > drivers/gpu/drm/drm_atomic_helper.c | 38 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > index afdc376aa7e7..92ae34bde44d 100644 > --- a/drivers/gpu/drm/drm_atomic_helper.c > +++ b/drivers/gpu/drm/drm_atomic_helper.c > @@ -841,6 +841,44 @@ int drm_atomic_helper_commit(struct drm_device *dev, > EXPORT_SYMBOL(drm_atomic_helper_commit); > > /** > + * DOC: implementing async commit > + * > + * For now the atomic helpers don't support async commit directly. If there is > + * real need it could be added though, using the dma-buf fence infrastructure > + * for generic synchronization with outstanding rendering. > + * > + * For now drivers have to implement async commit themselves, with the following > + * sequence being the recommended one: > + * > + * 1. Run drm_atomic_helper_prepare_planes() first. This is the only function > + * which commit needs to call which can fail, so we want to run it first and > + * synchronously. > + * > + * 2. Synchronize with any outstanding asynchronous commit worker threads which > + * might be affected the new state update. This can be done by either cancelling > + * or flushing the work items, depending upon whether the driver can deal with > + * cancelled updates. Note that it is important to ensure that the framebuffer > + * cleanup is still done when cancelling. > + * > + * For sufficient parallelism it is recommended to have a work item per crtc > + * (for updates which don't touch global state) and a global one. Then we only > + * need to synchronize with the crtc work items for changed crtcs and the global > + * work item, which allows nice concurrent updates on disjoint sets of crtcs. > + * > + * 3. The software state is updated synchronously with > + * drm_atomic_helper_swap_state. Doing this under the protection of all modeset > + * locks means concurrent callers never see inconsistent state. And doing this > + * while it's guaranteed that no relevant async worker runs means that async > + * workers do not need grab any locks. Actually they must not grab locks, for > + * otherwise the work flushing will deadlock. > + * > + * 4. Schedule a work item to do all subsequent steps, using the split-out > + * commit helpers: a) pre-plane commit b) plane commit c) post-plane commit and > + * then cleaning up the framebuffers after the old framebuffer is no longer > + * being displayed. > + */ > + > +/** > * drm_atomic_helper_prepare_planes - prepare plane resources after commit > * @dev: DRM device > * @state: atomic state object with old state structures > -- > 2.1.1 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > http://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
