diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index cb8578b..a4d8031 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1470,7 +1470,8 @@
 
 	if (!HAS_PCH_CPT(dev) &&
 	    I915_READ(intel_dp->output_reg) & DP_PIPEB_SELECT) {
-		struct intel_crtc *intel_crtc = to_intel_crtc(intel_dp->base.base.crtc);
+		struct drm_crtc *crtc = intel_dp->base.base.crtc;
+
 		/* Hardware workaround: leaving our transcoder select
 		 * set to transcoder B while it's off will prevent the
 		 * corresponding HDMI output on transcoder A.
@@ -1485,7 +1486,19 @@
 		/* Changes to enable or select take place the vblank
 		 * after being written.
 		 */
-		intel_wait_for_vblank(dev, intel_crtc->pipe);
+		if (crtc == NULL) {
+			/* We can arrive here never having been attached
+			 * to a CRTC, for instance, due to inheriting
+			 * random state from the BIOS.
+			 *
+			 * If the pipe is not running, play safe and
+			 * wait for the clocks to stabilise before
+			 * continuing.
+			 */
+			POSTING_READ(intel_dp->output_reg);
+			msleep(50);
+		} else
+			intel_wait_for_vblank(dev, to_intel_crtc(crtc)->pipe);
 	}
 
 	I915_WRITE(intel_dp->output_reg, DP & ~DP_PORT_EN);