backend/drm: add support for explicit sync APIs

backend/drm/atomic.c

@@ -1,6 +1,8 @@
 #define _POSIX_C_SOURCE 200809L
 #include <stdlib.h>
 #include <stdio.h>
+#include <unistd.h>
+#include <wlr/render/timeline.h>
 #include <wlr/util/log.h>
 #include <xf86drm.h>
 #include <xf86drmMode.h>
@@ -202,6 +204,41 @@ error:
 	atom->failed = true;
 }
 
+static int set_plane_in_fence_fd(struct atomic *atom, struct wlr_drm_plane *plane,
+		struct wlr_render_timeline *timeline, uint64_t src_point) {
+	if (!plane->props.in_fence_fd) {
+		wlr_log(WLR_ERROR, "Missing IN_FENCE_FD property");
+		goto error;
+	}
+
+	int sync_file_fd = wlr_render_timeline_export_sync_file(timeline, src_point);
+	if (sync_file_fd < 0) {
+		goto error;
+	}
+
+	atomic_add(atom, plane->id, plane->props.in_fence_fd, sync_file_fd);
+
+	return sync_file_fd;
+
+error:
+	wlr_log(WLR_ERROR, "Failed to set plane %"PRIu32" IN_FENCE_FD", plane->id);
+	atom->failed = true;
+	return -1;
+}
+
+static void set_crtc_out_fence_ptr(struct atomic *atom, struct wlr_drm_crtc *crtc,
+		int *fd_ptr) {
+	if (!crtc->props.out_fence_ptr) {
+		wlr_log(WLR_ERROR,
+			"CRTC %"PRIu32" is missing the OUT_FENCE_PTR property",
+			crtc->id);
+		atom->failed = true;
+		return;
+	}
+
+	atomic_add(atom, crtc->id, crtc->props.out_fence_ptr, (uintptr_t)fd_ptr);
+}
+
 static bool atomic_crtc_commit(struct wlr_drm_connector *conn,
 		const struct wlr_drm_connector_state *state, uint32_t flags,
 		bool test_only) {
@@ -273,6 +310,8 @@ static bool atomic_crtc_commit(struct wlr_drm_connector *conn,
 		flags |= DRM_MODE_ATOMIC_NONBLOCK;
 	}
 
+	int in_fence_fd = -1, out_fence_fd = -1;
+
 	struct atomic atom;
 	atomic_begin(&atom);
 	atomic_add(&atom, conn->id, conn->props.crtc_id, active ? crtc->id : 0);
@@ -301,6 +340,13 @@ static bool atomic_crtc_commit(struct wlr_drm_connector *conn,
 			atomic_add(&atom, crtc->primary->id,
 				crtc->primary->props.fb_damage_clips, fb_damage_clips);
 		}
+		if (state->base->committed & WLR_OUTPUT_STATE_WAIT_TIMELINE) {
+			in_fence_fd = set_plane_in_fence_fd(&atom, crtc->primary,
+				state->base->wait_timeline, state->base->wait_point);
+		}
+		if (state->base->committed & WLR_OUTPUT_STATE_SIGNAL_TIMELINE) {
+			set_crtc_out_fence_ptr(&atom, crtc, &out_fence_fd);
+		}
 		if (crtc->cursor) {
 			if (drm_connector_is_cursor_visible(conn)) {
 				set_plane_props(&atom, drm, crtc->cursor, crtc->id,
@@ -340,6 +386,14 @@ static bool atomic_crtc_commit(struct wlr_drm_connector *conn,
 		wlr_log_errno(WLR_ERROR, "Failed to destroy FB_DAMAGE_CLIPS property blob");
 	}
 
+	close(in_fence_fd);
+
+	if (out_fence_fd > 0) {
+		ok = wlr_render_timeline_import_sync_file(state->base->signal_timeline,
+			state->base->signal_point, out_fence_fd);
+		close(out_fence_fd);
+	}
+
 	return ok;
 }
 

backend/drm/drm.c

@@ -36,7 +36,9 @@ static const uint32_t COMMIT_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BUFFER |
 	WLR_OUTPUT_STATE_MODE |
 	WLR_OUTPUT_STATE_ENABLED |
-	WLR_OUTPUT_STATE_GAMMA_LUT;
+	WLR_OUTPUT_STATE_GAMMA_LUT |
+	WLR_OUTPUT_STATE_WAIT_TIMELINE |
+	WLR_OUTPUT_STATE_SIGNAL_TIMELINE;
 
 static const uint32_t SUPPORTED_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BACKEND_OPTIONAL | COMMIT_OUTPUT_STATE;
@@ -491,6 +493,13 @@ static bool drm_connector_test(struct wlr_output *output,
 		}
 	}
 
+	if ((output->pending.committed & (WLR_OUTPUT_STATE_WAIT_TIMELINE |
+			WLR_OUTPUT_STATE_SIGNAL_TIMELINE)) && conn->backend->parent) {
+		wlr_drm_conn_log(conn, WLR_DEBUG,
+			"Sync timelines are unsupported in multi-GPU mode");
+		return false;
+	}
+
 	struct wlr_drm_connector_state pending = {0};
 	drm_connector_state_init(&pending, conn, state);
 

backend/drm/legacy.c

@@ -54,6 +54,13 @@ static bool legacy_crtc_test(struct wlr_drm_connector *conn,
 		}
 	}
 
+	if (state->base->committed & (WLR_OUTPUT_STATE_WAIT_TIMELINE |
+			WLR_OUTPUT_STATE_SIGNAL_TIMELINE)) {
+		wlr_drm_conn_log(conn, WLR_DEBUG,
+			"Sync timelines are unsupported with legacy KMS interface");
+		return false;
+	}
+
 	return true;
 }
 

backend/drm/properties.c

@@ -41,6 +41,7 @@ static const struct prop_info crtc_info[] = {
 	{ "GAMMA_LUT", INDEX(gamma_lut) },
 	{ "GAMMA_LUT_SIZE", INDEX(gamma_lut_size) },
 	{ "MODE_ID", INDEX(mode_id) },
+	{ "OUT_FENCE_PTR", INDEX(out_fence_ptr) },
 	{ "VRR_ENABLED", INDEX(vrr_enabled) },
 #undef INDEX
 };
@@ -54,6 +55,7 @@ static const struct prop_info plane_info[] = {
 	{ "CRTC_Y", INDEX(crtc_y) },
 	{ "FB_DAMAGE_CLIPS", INDEX(fb_damage_clips) },
 	{ "FB_ID", INDEX(fb_id) },
+	{ "IN_FENCE_FD", INDEX(in_fence_fd) },
 	{ "IN_FORMATS", INDEX(in_formats) },
 	{ "SRC_H", INDEX(src_h) },
 	{ "SRC_W", INDEX(src_w) },

include/backend/drm/properties.h

@@ -41,6 +41,7 @@ union wlr_drm_crtc_props {
 
 		uint32_t active;
 		uint32_t mode_id;
+		uint32_t out_fence_ptr;
 	};
 	uint32_t props[6];
 };
@@ -64,6 +65,7 @@ union wlr_drm_plane_props {
 		uint32_t fb_id;
 		uint32_t crtc_id;
 		uint32_t fb_damage_clips;
+		uint32_t in_fence_fd;
 	};
 	uint32_t props[14];
 };