From cd555f9261d5443ba13f484fe4baa6dc3978c859 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?F=C3=A9lix=20Poisot?= <felix@lhfblc.fr>
Date: Fri, 31 Jan 2025 18:59:10 +0000
Subject: [PATCH] backend/drm: properly delay syncobj signalling

DRM CRTC signals when scanout begins, but
wlr_output_state_set_signal_timeline() is defined to signal buffer
release. Delay to the next page flip
---
 backend/drm/atomic.c      |  9 +++++++--
 backend/drm/drm.c         | 30 ++++++++++++++++++++++++++++++
 include/backend/drm/drm.h |  4 ++++
 3 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/backend/drm/atomic.c b/backend/drm/atomic.c
index 9bccff6ce..f12c56907 100644
--- a/backend/drm/atomic.c
+++ b/backend/drm/atomic.c
@@ -426,8 +426,13 @@ void drm_atomic_connector_apply_commit(struct wlr_drm_connector_state *state) {
 	}
 	if (state->out_fence_fd >= 0) {
 		// TODO: error handling
-		wlr_drm_syncobj_timeline_import_sync_file(state->base->signal_timeline,
-			state->base->signal_point, state->out_fence_fd);
+		if (crtc->primary->current_release_timeline != NULL) {
+			wlr_drm_syncobj_timeline_import_sync_file(crtc->primary->current_release_timeline,
+				crtc->primary->current_release_point, state->out_fence_fd);
+			wlr_drm_syncobj_timeline_unref(crtc->primary->current_release_timeline);
+			crtc->primary->current_release_timeline = NULL;
+			crtc->primary->current_release_point = 0;
+		}
 		close(state->out_fence_fd);
 	}
 
diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index 9b90022d2..7cfea5a14 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -368,7 +368,17 @@ static void drm_plane_finish_surface(struct wlr_drm_plane *plane) {
 	}
 
 	drm_fb_clear(&plane->queued_fb);
+	if (plane->queued_release_timeline != NULL) {
+		wlr_drm_syncobj_timeline_signal(plane->queued_release_timeline, plane->queued_release_point);
+		wlr_drm_syncobj_timeline_unref(plane->queued_release_timeline);
+		plane->queued_release_timeline = NULL;
+	}
 	drm_fb_clear(&plane->current_fb);
+	if (plane->current_release_timeline != NULL) {
+		wlr_drm_syncobj_timeline_signal(plane->current_release_timeline, plane->current_release_point);
+		wlr_drm_syncobj_timeline_unref(plane->current_release_timeline);
+		plane->current_release_timeline = NULL;
+	}
 
 	finish_drm_surface(&plane->mgpu_surf);
 }
@@ -557,6 +567,18 @@ static void drm_connector_apply_commit(const struct wlr_drm_connector_state *sta
 	struct wlr_drm_crtc *crtc = conn->crtc;
 
 	drm_fb_copy(&crtc->primary->queued_fb, state->primary_fb);
+	if (crtc->primary->queued_release_timeline != NULL) {
+		wlr_drm_syncobj_timeline_signal(crtc->primary->queued_release_timeline, crtc->primary->queued_release_point);
+		wlr_drm_syncobj_timeline_unref(crtc->primary->queued_release_timeline);
+	}
+	if (state->base->signal_timeline != NULL) {
+		crtc->primary->queued_release_timeline = wlr_drm_syncobj_timeline_ref(state->base->signal_timeline);
+		crtc->primary->queued_release_point = state->base->signal_point;
+	} else {
+		crtc->primary->queued_release_timeline = NULL;
+		crtc->primary->queued_release_point = 0;
+	}
+
 	crtc->primary->viewport = state->primary_viewport;
 	if (crtc->cursor != NULL) {
 		drm_fb_copy(&crtc->cursor->queued_fb, state->cursor_fb);
@@ -2019,6 +2041,14 @@ static void handle_page_flip(int fd, unsigned seq,
 	struct wlr_drm_plane *plane = conn->crtc->primary;
 	if (plane->queued_fb) {
 		drm_fb_move(&plane->current_fb, &plane->queued_fb);
+		if (plane->current_release_timeline != NULL) {
+			wlr_drm_syncobj_timeline_signal(plane->current_release_timeline, plane->current_release_point);
+			wlr_drm_syncobj_timeline_unref(plane->current_release_timeline);
+		}
+		plane->current_release_timeline = plane->queued_release_timeline;
+		plane->current_release_point = plane->queued_release_point;
+		plane->queued_release_timeline = NULL;
+		plane->queued_release_point = 0;
 	}
 	if (conn->crtc->cursor && conn->crtc->cursor->queued_fb) {
 		drm_fb_move(&conn->crtc->cursor->current_fb,
diff --git a/include/backend/drm/drm.h b/include/backend/drm/drm.h
index af4231f54..e07c16efe 100644
--- a/include/backend/drm/drm.h
+++ b/include/backend/drm/drm.h
@@ -29,8 +29,12 @@ struct wlr_drm_plane {
 
 	/* Buffer submitted to the kernel, will be presented on next vblank */
 	struct wlr_drm_fb *queued_fb;
+	struct wlr_drm_syncobj_timeline *queued_release_timeline;
+	uint64_t queued_release_point;
 	/* Buffer currently displayed on screen */
 	struct wlr_drm_fb *current_fb;
+	struct wlr_drm_syncobj_timeline *current_release_timeline;
+	uint64_t current_release_point;
 	/* Viewport belonging to the last committed fb */
 	struct wlr_drm_viewport viewport;