drm: apple: Only use swap timestamps if VRR is actually active

macOS is inconsistent with how it uses DCP timestamps. Some swaps
don't use them at all. We know they are required for VRR display
modes to work properly, so let's just turn them on when we are
connected to a VRR display. This includes the 120 Hz mode on
the 14" and 16" MacBook Pros.

Signed-off-by: James Calligeros <[email protected]>

Author: chadmed

drivers/gpu/drm/apple/iomfb_template.c

@@ -1247,8 +1247,8 @@ int DCP_FW_NAME(iomfb_modeset)(struct apple_dcp *dcp,
 		.timing_mode_id = mode->timing_mode_id
 	};
 
-	/* Keep track of suspected vrr modes */
-	dcp->use_timestamps = mode->vrr;
+	/* Use DCP swap timestamps on MacBook Pros with VRR */
+	dcp->use_timestamps = mode->vrr && dcp->main_display;
 
 	cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
 	if (!cookie) {
@@ -1422,7 +1422,7 @@ void DCP_FW_NAME(iomfb_flush)(struct apple_dcp *dcp, struct drm_crtc *crtc, stru
 		req->clear = 1;
 	}
 
-	if (has_surface && dcp->use_timestamps) {
+	if (has_surface && (dcp->use_timestamps || crtc_state->vrr_enabled)) {
 		/*
 		 * TODO: ascertain with certainty what these timestamps
 		 * are. They are something to do with presentation timing,