drm: call drm_gem_object_funcs.mmap with fake offset

The fake offset is going to stay, so change the calling convention for
drm_gem_object_funcs.mmap to include the fake offset.  Update all users
accordingly.

Note that this reverts 83b8a6f242 ("drm/gem: Fix mmap fake offset
handling for drm_gem_object_funcs.mmap") and on top then adds the fake
offset to  drm_gem_prime_mmap to make sure all paths leading to
obj->funcs->mmap are consistent.

v3: move fake-offset tweak in drm_gem_prime_mmap() so we have this code
    only once in the function (Rob Herring).

Fixes: 83b8a6f242 ("drm/gem: Fix mmap fake offset handling for drm_gem_object_funcs.mmap")
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20191127092523.5620-2-kraxel@redhat.com

drivers/gpu/drm/drm_gem.c

@@ -1106,9 +1106,6 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
 		return -EINVAL;
 
 	if (obj->funcs && obj->funcs->mmap) {
-		/* Remove the fake offset */
-		vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);
-
 		ret = obj->funcs->mmap(obj, vma);
 		if (ret)
 			return ret;

drivers/gpu/drm/drm_gem_shmem_helper.c

@@ -528,6 +528,9 @@ int drm_gem_shmem_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 	struct drm_gem_shmem_object *shmem;
 	int ret;
 
+	/* Remove the fake offset */
+	vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);
+
 	shmem = to_drm_gem_shmem_obj(obj);
 
 	ret = drm_gem_shmem_get_pages(shmem);

drivers/gpu/drm/drm_prime.c

@@ -713,6 +713,9 @@ int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 	struct file *fil;
 	int ret;
 
+	/* Add the fake offset */
+	vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);
+
 	if (obj->funcs && obj->funcs->mmap) {
 		ret = obj->funcs->mmap(obj, vma);
 		if (ret)
@@ -737,8 +740,6 @@ int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 	if (ret)
 		goto out;
 
-	vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);
-
 	ret = obj->dev->driver->fops->mmap(fil, vma);
 
 	drm_vma_node_revoke(&obj->vma_node, priv);

drivers/gpu/drm/ttm/ttm_bo_vm.c

@@ -514,13 +514,6 @@ EXPORT_SYMBOL(ttm_bo_mmap);
 int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
 {
 	ttm_bo_get(bo);
-
-	/*
-	 * FIXME: &drm_gem_object_funcs.mmap is called with the fake offset
-	 * removed. Add it back here until the rest of TTM works without it.
-	 */
-	vma->vm_pgoff += drm_vma_node_start(&bo->base.vma_node);
-
 	ttm_bo_mmap_vma_setup(bo, vma);
 	return 0;
 }

include/drm/drm_gem.h

@@ -159,9 +159,7 @@ struct drm_gem_object_funcs {
 	 *
 	 * The callback is used by by both drm_gem_mmap_obj() and
 	 * drm_gem_prime_mmap().  When @mmap is present @vm_ops is not
-	 * used, the @mmap callback must set vma->vm_ops instead. The @mmap
-	 * callback is always called with a 0 offset. The caller will remove
-	 * the fake offset as necessary.
+	 * used, the @mmap callback must set vma->vm_ops instead.
 	 */
 	int (*mmap)(struct drm_gem_object *obj, struct vm_area_struct *vma);