--- ./drivers/gpu/drm/drm_vblank.c.vanilla	2026-03-11 19:56:04.616769337 +0100
+++ ./drivers/gpu/drm/drm_vblank.c	2026-03-11 20:38:14.557361947 +0100
@@ -300,12 +300,12 @@
 static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
 				    bool in_vblank_irq)
 {
-	struct drm_vblank_crtc *vblank = drm_vblank_crtc(dev, pipe);
+	struct drm_vblank_crtc *vblank = NULL;
 	u32 cur_vblank, diff;
 	bool rc;
 	ktime_t t_vblank;
 	int count = DRM_TIMESTAMP_MAXRETRIES;
-	int framedur_ns = vblank->framedur_ns;
+	int framedur_ns = 0;
 	u32 max_vblank_count = drm_max_vblank_count(dev, pipe);
 
 	/*
@@ -325,10 +325,14 @@
 		rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, in_vblank_irq);
 	} while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);
 
-	if (max_vblank_count) {
+	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+		vblank = drm_vblank_crtc(dev, pipe);
+		framedur_ns = vblank->framedur_ns;
+
+	  if (max_vblank_count) {
 		/* trust the hw counter when it's around */
 		diff = (cur_vblank - vblank->last) & max_vblank_count;
-	} else if (rc && framedur_ns) {
+	  } else if (rc && framedur_ns) {
 		u64 diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));
 
 		/*
@@ -346,35 +350,36 @@
 		if (diff == 0 && in_vblank_irq)
 			drm_dbg_vbl(dev, "crtc %u: Redundant vblirq ignored\n",
 				    pipe);
-	} else {
+	  } else {
 		/* some kind of default for drivers w/o accurate vbl timestamping */
 		diff = in_vblank_irq ? 1 : 0;
-	}
+	  }
 
-	/*
-	 * Within a drm_vblank_pre_modeset - drm_vblank_post_modeset
-	 * interval? If so then vblank irqs keep running and it will likely
-	 * happen that the hardware vblank counter is not trustworthy as it
-	 * might reset at some point in that interval and vblank timestamps
-	 * are not trustworthy either in that interval. Iow. this can result
-	 * in a bogus diff >> 1 which must be avoided as it would cause
-	 * random large forward jumps of the software vblank counter.
-	 */
-	if (diff > 1 && (vblank->inmodeset & 0x2)) {
+	  /*
+	   * Within a drm_vblank_pre_modeset - drm_vblank_post_modeset
+	   * interval? If so then vblank irqs keep running and it will likely
+	   * happen that the hardware vblank counter is not trustworthy as it
+	   * might reset at some point in that interval and vblank timestamps
+	   * are not trustworthy either in that interval. Iow. this can result
+	   * in a bogus diff >> 1 which must be avoided as it would cause
+	   * random large forward jumps of the software vblank counter.
+	   */
+	  if (diff > 1 && (vblank->inmodeset & 0x2)) {
 		drm_dbg_vbl(dev,
 			    "clamping vblank bump to 1 on crtc %u: diffr=%u"
 			    " due to pre-modeset.\n", pipe, diff);
 		diff = 1;
-	}
+	  }
 
-	drm_dbg_vbl(dev, "updating vblank count on crtc %u:"
+	  drm_dbg_vbl(dev, "updating vblank count on crtc %u:"
 		    " current=%llu, diff=%u, hw=%u hw_last=%u\n",
 		    pipe, (unsigned long long)atomic64_read(&vblank->count),
 		    diff, cur_vblank, vblank->last);
 
-	if (diff == 0) {
+	 if (diff == 0) {
 		drm_WARN_ON_ONCE(dev, cur_vblank != vblank->last);
 		return;
+	  }
 	}
 
 	/*
@@ -913,9 +918,13 @@
 drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
 			  ktime_t *tvblank, bool in_vblank_irq)
 {
-	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
+	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
+
+		return drm_crtc_get_last_vbltimestamp(crtc, tvblank, in_vblank_irq);
+	}
 
-	return drm_crtc_get_last_vbltimestamp(crtc, tvblank, in_vblank_irq);
+	return false;
 }
 
 /**
@@ -1986,7 +1995,6 @@
 
 static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe)
 {
-	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
 	bool high_prec = false;
 	struct drm_pending_vblank_event *e, *t;
 	ktime_t now;
@@ -2010,8 +2018,12 @@
 		send_vblank_event(dev, e, seq, now);
 	}
 
-	if (crtc && crtc->funcs->get_vblank_timestamp)
-		high_prec = true;
+	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
+
+		if (crtc && crtc->funcs->get_vblank_timestamp)
+			high_prec = true;
+	}
 
 	trace_drm_vblank_event(pipe, seq, now, high_prec);
 }