1 files changed, 69 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 72ee3cd96a24..edef30be8304 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -526,6 +526,75 @@ static int __drm_buddy_alloc_range(struct drm_buddy *mm,
 }
 
 /**
+ * drm_buddy_block_trim - free unused pages
+ *
+ * @mm: DRM buddy manager
+ * @new_size: original size requested
+ * @blocks: Input and output list of allocated blocks.
+ * MUST contain single block as input to be trimmed.
+ * On success will contain the newly allocated blocks
+ * making up the @new_size. Blocks always appear in
+ * ascending order
+ *
+ * For contiguous allocation, we round up the size to the nearest
+ * power of two value, drivers consume *actual* size, so remaining
+ * portions are unused and can be optionally freed with this function
+ *
+ * Returns:
+ * 0 on success, error code on failure.
+ */
+int drm_buddy_block_trim(struct drm_buddy *mm,
+			 u64 new_size,
+			 struct list_head *blocks)
+{
+	struct drm_buddy_block *parent;
+	struct drm_buddy_block *block;
+	LIST_HEAD(dfs);
+	u64 new_start;
+	int err;
+
+	if (!list_is_singular(blocks))
+		return -EINVAL;
+
+	block = list_first_entry(blocks,
+				 struct drm_buddy_block,
+				 link);
+
+	if (WARN_ON(!drm_buddy_block_is_allocated(block)))
+		return -EINVAL;
+
+	if (new_size > drm_buddy_block_size(mm, block))
+		return -EINVAL;
+
+	if (!new_size || !IS_ALIGNED(new_size, mm->chunk_size))
+		return -EINVAL;
+
+	if (new_size == drm_buddy_block_size(mm, block))
+		return 0;
+
+	list_del(&block->link);
+	mark_free(mm, block);
+	mm->avail += drm_buddy_block_size(mm, block);
+
+	/* Prevent recursively freeing this node */
+	parent = block->parent;
+	block->parent = NULL;
+
+	new_start = drm_buddy_block_offset(block);
+	list_add(&block->tmp_link, &dfs);
+	err =  __alloc_range(mm, &dfs, new_start, new_size, blocks);
+	if (err) {
+		mark_allocated(block);
+		mm->avail -= drm_buddy_block_size(mm, block);
+		list_add(&block->link, blocks);
+	}
+
+	block->parent = parent;
+	return err;
+}
+EXPORT_SYMBOL(drm_buddy_block_trim);
+
+/**
  * drm_buddy_alloc_blocks - allocate power-of-two blocks
  *
  * @mm: DRM buddy manager to allocate from