drm/armada: don't abuse DMA_ERROR_CODE

dev_addr isn't even a dma_addr_t, and DMA_ERROR_CODE has never been
a valid driver API.  Add a bool mapped flag instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/gpu/drm/armada/armada_fb.c

@@ -133,7 +133,7 @@ static struct drm_framebuffer *armada_fb_create(struct drm_device *dev,
 	}
 
 	/* Framebuffer objects must have a valid device address for scanout */
-	if (obj->dev_addr == DMA_ERROR_CODE) {
+	if (!obj->mapped) {
 		ret = -EINVAL;
 		goto err_unref;
 	}

drivers/gpu/drm/armada/armada_gem.c

@@ -175,6 +175,7 @@ armada_gem_linear_back(struct drm_device *dev, struct armada_gem_object *obj)
 
 		obj->phys_addr = obj->linear->start;
 		obj->dev_addr = obj->linear->start;
+		obj->mapped = true;
 	}
 
 	DRM_DEBUG_DRIVER("obj %p phys %#llx dev %#llx\n", obj,
@@ -205,7 +206,6 @@ armada_gem_alloc_private_object(struct drm_device *dev, size_t size)
 		return NULL;
 
 	drm_gem_private_object_init(dev, &obj->obj, size);
-	obj->dev_addr = DMA_ERROR_CODE;
 
 	DRM_DEBUG_DRIVER("alloc private obj %p size %zu\n", obj, size);
 
@@ -229,8 +229,6 @@ static struct armada_gem_object *armada_gem_alloc_object(struct drm_device *dev,
 		return NULL;
 	}
 
-	obj->dev_addr = DMA_ERROR_CODE;
-
 	mapping = obj->obj.filp->f_mapping;
 	mapping_set_gfp_mask(mapping, GFP_HIGHUSER | __GFP_RECLAIMABLE);
 
@@ -610,5 +608,6 @@ int armada_gem_map_import(struct armada_gem_object *dobj)
 		return -EINVAL;
 	}
 	dobj->dev_addr = sg_dma_address(dobj->sgt->sgl);
+	dobj->mapped = true;
 	return 0;
 }

drivers/gpu/drm/armada/armada_gem.h

@@ -16,6 +16,7 @@ struct armada_gem_object {
 	void			*addr;
 	phys_addr_t		phys_addr;
 	resource_size_t		dev_addr;
+	bool			mapped;
 	struct drm_mm_node	*linear;	/* for linear backed */
 	struct page		*page;		/* for page backed */
 	struct sg_table		*sgt;		/* for imported */