drm/nouveau: fix null ptr dereferences on some boards

Regression from "device: populate master subdev pointer only when fully
constructed"

Reported-by: Bob Gleitsmann <rjgleits@bellsouth.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/gpu/drm/nouveau/core/include/subdev/instmem.h b/drivers/gpu/drm/nouveau/core/include/subdev/instmem.h
index ec7a54e..4aca338 100644
--- a/drivers/gpu/drm/nouveau/core/include/subdev/instmem.h
+++ b/drivers/gpu/drm/nouveau/core/include/subdev/instmem.h
@@ -50,6 +50,13 @@ struct nouveau_instmem {
 static inline struct nouveau_instmem *
 nouveau_instmem(void *obj)
 {
+	/* nv04/nv40 impls need to create objects in their constructor,
+	 * which is before the subdev pointer is valid
+	 */
+	if (nv_iclass(obj, NV_SUBDEV_CLASS) &&
+	    nv_subidx(obj) == NVDEV_SUBDEV_INSTMEM)
+		return obj;
+
 	return (void *)nv_device(obj)->subdev[NVDEV_SUBDEV_INSTMEM];
 }