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authorSimon Ser <contact@emersion.fr>2024-02-14 20:04:22 +0100
committerSimon Ser <contact@emersion.fr>2024-02-15 09:56:33 +0100
commit17fe87af5e1a5fded8a210a2e6b281804d57bebe (patch)
tree4f7f0fb8df107f6e061a3298514a12e6fdb9793d /backend
parent653e28d2a303304a280bd7fa51acbe27299b44d7 (diff)
backend/drm: skip reset after VT switch if possible
If all connectors and planes already have the right CRTC set, or are disabled, we can skip the device-wide reset after a VT switch. I've contemplated using a more fine-grained logic to only reset the connectors, CRTCs and planes that need to be migrated. However, writing a correct algorithm for this would be quite involved, and it doesn't seem worth the trouble anyways. Closes: https://github.com/swaywm/sway/issues/7956
Diffstat (limited to 'backend')
-rw-r--r--backend/drm/drm.c64
1 files changed, 63 insertions, 1 deletions
diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index fe5f4f8f..42080603 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -1738,6 +1738,68 @@ static void build_current_connector_state(struct wlr_output_state *state,
}
}
+/**
+ * Check whether we need to perform a full reset after a VT switch.
+ *
+ * If any connector or plane has a different CRTC, we need to perform a full
+ * reset to restore our mapping. We couldn't avoid a full reset even if we
+ * used a single KMS atomic commit to apply our state: the kernel rejects
+ * commits which migrate a plane from one CRTC to another without going through
+ * an intermediate state where the plane is disabled.
+ */
+static bool skip_reset_for_restore(struct wlr_drm_backend *drm) {
+ struct wlr_drm_connector *conn;
+ wl_list_for_each(conn, &drm->connectors, link) {
+ drmModeConnector *drm_conn = drmModeGetConnectorCurrent(drm->fd, conn->id);
+ if (drm_conn == NULL) {
+ return false;
+ }
+ struct wlr_drm_crtc *crtc = connector_get_current_crtc(conn, drm_conn);
+ drmModeFreeConnector(drm_conn);
+
+ if (crtc != NULL && conn->crtc != crtc) {
+ return false;
+ }
+ }
+
+ for (size_t i = 0; i < drm->num_planes; i++) {
+ struct wlr_drm_plane *plane = &drm->planes[i];
+
+ drmModePlane *drm_plane = drmModeGetPlane(drm->fd, plane->id);
+ if (drm_plane == NULL) {
+ return false;
+ }
+ uint32_t crtc_id = drm_plane->crtc_id;
+ drmModeFreePlane(drm_plane);
+
+ struct wlr_drm_crtc *crtc = NULL;
+ for (size_t i = 0; i < drm->num_crtcs; i++) {
+ if (drm->crtcs[i].id == crtc_id) {
+ crtc = &drm->crtcs[i];
+ break;
+ }
+ }
+ if (crtc == NULL) {
+ continue;
+ }
+
+ bool ok = false;
+ switch (plane->type) {
+ case DRM_PLANE_TYPE_PRIMARY:
+ ok = crtc->primary == plane;
+ break;
+ case DRM_PLANE_TYPE_CURSOR:
+ ok = crtc->cursor == plane;
+ break;
+ }
+ if (!ok) {
+ return false;
+ }
+ }
+
+ return true;
+}
+
void restore_drm_device(struct wlr_drm_backend *drm) {
// The previous DRM master leaves KMS in an undefined state. We need
// to restore our own state, but be careful to avoid invalid
@@ -1745,7 +1807,7 @@ void restore_drm_device(struct wlr_drm_backend *drm) {
// first disable all CRTCs, then light up the ones we were using
// before the VT switch.
// TODO: better use the atomic API to improve restoration after a VT switch
- if (!drm->iface->reset(drm)) {
+ if (!skip_reset_for_restore(drm) && !drm->iface->reset(drm)) {
wlr_log(WLR_ERROR, "Failed to reset state after VT switch");
}