drm/nouveau/fbcon: fix oops without fbdev emulation

BugLink: https://bugs.launchpad.net/bugs/1810807

[ Upstream commit 48137663 ]

This is similar to an earlier commit 52dfcc5c ("drm/nouveau: fix for
disabled fbdev emulation"), but protects all occurrences of helper.fbdev
in the source.

I see oops in nouveau_fbcon_accel_save_disable() called from
nouveau_fbcon_set_suspend_work() on Linux 3.13 when
CONFIG_DRM_FBDEV_EMULATION option is disabled.
Signed-off-by: Pavel Roskin <plroskin@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/gpu/drm/nouveau/nouveau_fbcon.c

@@ -235,7 +235,7 @@ 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;
 	}
@@ -245,7 +245,7 @@ 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;
 	}
 }
@@ -257,6 +257,7 @@ nouveau_fbcon_accel_fini(struct drm_device *dev)
 	struct nouveau_fbdev *fbcon = drm->fbcon;
 	if (fbcon && drm->channel) {
 		console_lock();
+		if (fbcon->helper.fbdev)
 			fbcon->helper.fbdev->flags |= FBINFO_HWACCEL_DISABLED;
 		console_unlock();
 		nouveau_channel_idle(drm->channel);