drm/nouveau: don't munge in drm_mm internals

Nouveau was checking drm_mm internals on teardown to see whether the
memory manager was initialized. Hide these internals in a small
inline helper function.
Acked-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/nouveau/nouveau_object.c

@@ -909,7 +909,7 @@ nouveau_gpuobj_channel_takedown(struct nouveau_channel *chan)
 	nouveau_vm_ref(NULL, &chan->vm, chan->vm_pd);
 	nouveau_gpuobj_ref(NULL, &chan->vm_pd);
 
-	if (chan->ramin_heap.free_stack.next)
+	if (drm_mm_initialized(&chan->ramin_heap))
 		drm_mm_takedown(&chan->ramin_heap);
 	nouveau_gpuobj_ref(NULL, &chan->ramin);
 }

drivers/gpu/drm/nouveau/nv50_instmem.c

@@ -56,7 +56,7 @@ nv50_channel_del(struct nouveau_channel **pchan)
 	nouveau_gpuobj_ref(NULL, &chan->ramfc);
 	nouveau_vm_ref(NULL, &chan->vm, chan->vm_pd);
 	nouveau_gpuobj_ref(NULL, &chan->vm_pd);
-	if (chan->ramin_heap.free_stack.next)
+	if (drm_mm_initialized(&chan->ramin_heap))
 		drm_mm_takedown(&chan->ramin_heap);
 	nouveau_gpuobj_ref(NULL, &chan->ramin);
 	kfree(chan);
@@ -259,7 +259,7 @@ nv50_instmem_takedown(struct drm_device *dev)
 	nouveau_gpuobj_ref(NULL, &dev_priv->bar3_vm->pgt[0].obj[0]);
 	nouveau_vm_ref(NULL, &dev_priv->bar3_vm, NULL);
 
-	if (dev_priv->ramin_heap.free_stack.next)
+	if (drm_mm_initialized(&dev_priv->ramin_heap))
 		drm_mm_takedown(&dev_priv->ramin_heap);
 
 	dev_priv->engine.instmem.priv = NULL;

drivers/gpu/drm/nouveau/nvc0_instmem.c

@@ -67,7 +67,7 @@ nvc0_channel_del(struct nouveau_channel **pchan)
 		return;
 
 	nouveau_vm_ref(NULL, &chan->vm, NULL);
-	if (chan->ramin_heap.free_stack.next)
+	if (drm_mm_initialized(&chan->ramin_heap))
 		drm_mm_takedown(&chan->ramin_heap);
 	nouveau_gpuobj_ref(NULL, &chan->ramin);
 	kfree(chan);

include/drm/drm_mm.h

@@ -72,6 +72,11 @@ struct drm_mm {
 	unsigned long scan_end;
 };
 
+static inline bool drm_mm_initialized(struct drm_mm *mm)
+{
+	return mm->free_stack.next;
+}
+
 /*
  * Basic range manager support (drm_mm.c)
  */