From 0e6176c6d286316e9431b4f695940cfac4ffe6c2 Mon Sep 17 00:00:00 2001
From: Ben Skeggs <bskeggs@redhat.com>
Date: Tue, 28 Jan 2020 14:39:26 +1000
Subject: [PATCH] drm/nouveau/disp/nv50-: prevent oops when no channel method map provided
Git-commit: 0e6176c6d286316e9431b4f695940cfac4ffe6c2
Patch-mainline: v5.6-rc1
References: bsc#1051510

The implementations for most channel types contains a map of methods to
priv registers in order to provide debugging info when a disp exception
has been raised.

This info is missing from the implementation of PIO channels as they're
rather simplistic already, however, if an exception is raised by one of
them, we'd end up triggering a NULL-pointer deref.  Not ideal...

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=206299
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c b/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
index bcf32d92ee5a..50e3539f33d2 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
@@ -74,6 +74,8 @@ nv50_disp_chan_mthd(struct nv50_disp_chan *chan, int debug)
 
 	if (debug > subdev->debug)
 		return;
+	if (!mthd)
+		return;
 
 	for (i = 0; (list = mthd->data[i].mthd) != NULL; i++) {
 		u32 base = chan->head * mthd->addr;
-- 
2.16.4