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@gmail.com Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch --- 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