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backend/drm: skip reset after VT switch if possible

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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
This commit is contained in:
Simon Ser 2024-02-14 20:04:22 +01:00
parent 653e28d2a3
commit 17fe87af5e
1 changed files with 63 additions and 1 deletions
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64
backend/drm/drm.c
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@ -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");
}