drm/i915/fbc: keep FBC disabled if selective update is on in xe2lpd

FBC was disabled in case PSR2 selective update in display 12 to
14 as part of a wa. From xe2lpd onwards there is a logic to be
implemented to decide between FBC and selective update. Until
that logic is implemented keep FBC disabled in case selective
update is enabled.

v1: updated patch description and some explanation and todo

Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250321094529.197397-2-vinod.govindapillai@intel.com

drivers/gpu/drm/i915/display/intel_fbc.c

@@ -1465,13 +1465,15 @@ static int intel_fbc_check_plane(struct intel_atomic_state *state,
 	 * Recommendation is to keep this combination disabled
 	 * Bspec: 50422 HSD: 14010260002
 	 *
-	 * In Xe3, PSR2 selective fetch and FBC dirty rect feature cannot
-	 * coexist. So if PSR2 selective fetch is supported then mark that
-	 * FBC is not supported.
-	 * TODO: Need a logic to decide between PSR2 and FBC Dirty rect
+	 * TODO: Implement a logic to select between PSR2 selective fetch and
+	 * FBC based on Bspec: 68881 in xe2lpd onwards.
+	 *
+	 * As we still see some strange underruns in those platforms while
+	 * disabling PSR2, keep FBC disabled in case of selective update is on
+	 * until the selection logic is implemented.
 	 */
-	if ((IS_DISPLAY_VER(display, 12, 14) || HAS_FBC_DIRTY_RECT(display)) &&
-	    crtc_state->has_sel_update && !crtc_state->has_panel_replay) {
+	if (DISPLAY_VER(display) >= 12 && crtc_state->has_sel_update &&
+	    !crtc_state->has_panel_replay) {
 		plane_state->no_fbc_reason = "PSR2 enabled";
 		return 0;
 	}