From 227f66d2f9954f68375736af62ebcd73c6754d69 Mon Sep 17 00:00:00 2001
From: Ben Skeggs <bskeggs@redhat.com>
Date: Tue, 3 Oct 2017 16:24:28 +1000
Subject: [PATCH] drm/nouveau/kms/nv50: fix oops during DP IRQ handling on non-MST boards
Git-commit: 227f66d2f9954f68375736af62ebcd73c6754d69
Patch-mainline: v4.14-rc6
References: bsc#1051510

Reported-by: Woody Suwalski <terraluna977@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/nouveau/nv50_display.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/nouveau/nv50_display.c
+++ b/drivers/gpu/drm/nouveau/nv50_display.c
@@ -3265,11 +3265,14 @@ nv50_mstm = {
 void
 nv50_mstm_service(struct nv50_mstm *mstm)
 {
-	struct drm_dp_aux *aux = mstm->mgr.aux;
+	struct drm_dp_aux *aux = mstm ? mstm->mgr.aux : NULL;
 	bool handled = true;
 	int ret;
 	u8 esi[8] = {};
 
+	if (!aux)
+		return;
+
 	while (handled) {
 		ret = drm_dp_dpcd_read(aux, DP_SINK_COUNT_ESI, esi, 8);
 		if (ret != 8) {