drm/atomic: Add struct drm_crtc_commit to track async updates

Split out from my big nonblocking atomic commit helper code as prep
work. While add it, also add some neat asciiart to document how it's
supposed to be used.

v2: Resurrect misplaced hunk in the kerneldoc.

v3: Wording improvements from Liviu.

Tested-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Tomeu Vizoso <tomeu.vizoso@gmail.com>
Cc: Daniel Stone <daniels@collabora.com>
Tested-by: Liviu Dudau <Liviu.Dudau@arm.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465388359-8070-8-git-send-email-daniel.vetter@ffwll.ch
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 5e4b820..d99ab2f 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -33,6 +33,20 @@
 
 #include "drm_crtc_internal.h"
 
+static void crtc_commit_free(struct kref *kref)
+{
+	struct drm_crtc_commit *commit =
+		container_of(kref, struct drm_crtc_commit, ref);
+
+	kfree(commit);
+}
+
+void drm_crtc_commit_put(struct drm_crtc_commit *commit)
+{
+	kref_put(&commit->ref, crtc_commit_free);
+}
+EXPORT_SYMBOL(drm_crtc_commit_put);
+
 /**
  * drm_atomic_state_default_release -
  * release memory initialized by drm_atomic_state_init
@@ -148,6 +162,14 @@
 
 		crtc->funcs->atomic_destroy_state(crtc,
 						  state->crtcs[i].state);
+
+		if (state->crtcs[i].commit) {
+			kfree(state->crtcs[i].commit->event);
+			state->crtcs[i].commit->event = NULL;
+			drm_crtc_commit_put(state->crtcs[i].commit);
+		}
+
+		state->crtcs[i].commit = NULL;
 		state->crtcs[i].ptr = NULL;
 		state->crtcs[i].state = NULL;
 	}
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index aeb5d9e..4ec35f9 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -638,6 +638,9 @@
 	crtc->dev = dev;
 	crtc->funcs = funcs;
 
+	INIT_LIST_HEAD(&crtc->commit_list);
+	spin_lock_init(&crtc->commit_lock);
+
 	drm_modeset_lock_init(&crtc->mutex);
 	ret = drm_mode_object_get(dev, &crtc->base, DRM_MODE_OBJECT_CRTC);
 	if (ret)
diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index 64121f5..a27bc7cd 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -797,6 +797,12 @@
 {
 	assert_spin_locked(&dev->event_lock);
 
+	if (e->completion) {
+		/* ->completion might disappear as soon as it signalled. */
+		complete_all(e->completion);
+		e->completion = NULL;
+	}
+
 	if (e->fence) {
 		fence_signal(e->fence);
 		fence_put(e->fence);