[PATCH] drm/nouveau/fbcon: fix oops without fbdev emulation

[Pavel Roskin <plroskin@gmail.com>]

This is similar to an earlier commit 52dfcc5ccfbb ("drm/nouveau: fix for
disabled fbdev emulation"), but protects all other occurrences of
helper.fbdev in the source.

I see an oops in nouveau_fbcon_accel_save_disable() called from
nouveau_fbcon_set_suspend_work() on Linux 4.13 and 4.14-rc2 when
CONFIG_DRM_FBDEV_EMULATION option is disabled. It happens during gdm
login.

Linux 4.14-rc2 is affected even if CONFIG_DRM_FBDEV_EMULATION is enabled,
but no monitors are connected to the dock on a laptop with a discrete
NVIDIA card.

Signed-off-by: Pavel Roskin <plroskin@gmail.com>
---
 drivers/gpu/drm/nouveau/nouveau_fbcon.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_fbcon.c b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
index f7707849bb53..698b8b10b646 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
@@ -223,7 +223,7 @@ void
 nouveau_fbcon_accel_save_disable(struct drm_device *dev)
 {
 	struct nouveau_drm *drm = nouveau_drm(dev);
-	if (drm->fbcon) {
+	if (drm->fbcon && drm->fbcon->helper.fbdev) {
 		drm->fbcon->saved_flags = drm->fbcon->helper.fbdev->flags;
 		drm->fbcon->helper.fbdev->flags |= FBINFO_HWACCEL_DISABLED;
 	}
@@ -233,9 +233,8 @@ void
 nouveau_fbcon_accel_restore(struct drm_device *dev)
 {
 	struct nouveau_drm *drm = nouveau_drm(dev);
-	if (drm->fbcon) {
+	if (drm->fbcon && drm->fbcon->helper.fbdev)
 		drm->fbcon->helper.fbdev->flags = drm->fbcon->saved_flags;
-	}
 }
 
 static void
@@ -245,7 +244,8 @@ nouveau_fbcon_accel_fini(struct drm_device *dev)
 	struct nouveau_fbdev *fbcon = drm->fbcon;
 	if (fbcon && drm->channel) {
 		console_lock();
-		fbcon->helper.fbdev->flags |= FBINFO_HWACCEL_DISABLED;
+		if (drm->fbcon->helper.fbdev)
+			fbcon->helper.fbdev->flags |= FBINFO_HWACCEL_DISABLED;
 		console_unlock();
 		nouveau_channel_idle(drm->channel);
 		nvif_object_fini(&fbcon->twod);
-- 
2.14.1

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