drm/nouveau: allow creation of zero-sized mm

Useful for places where a given chipset may or may not have a given
resource, and we want to avoid having to spray checks for the mm's
existance around everywhere.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

2 files changed, 6 insertions, 4 deletions

diff --git a/drivers/gpu/drm/nouveau/core/core/mm.c b/drivers/gpu/drm/nouveau/core/core/mm.c
index 4d6206448670..a6d3cd6490f7 100644
--- a/drivers/gpu/drm/nouveau/core/core/mm.c
+++ b/drivers/gpu/drm/nouveau/core/core/mm.c
@@ -218,13 +218,16 @@ nouveau_mm_init(struct nouveau_mm *mm, u32 offset, u32 length, u32 block)
         node = kzalloc(sizeof(*node), GFP_KERNEL);
         if (!node)
                 return -ENOMEM;
-        node->offset = roundup(offset, mm->block_size);
-        node->length = rounddown(offset + length, mm->block_size) - node->offset;
+
+        if (length) {
+                node->offset  = roundup(offset, mm->block_size);
+                node->length  = rounddown(offset + length, mm->block_size);
+                node->length -= node->offset;
+        }
 
         list_add_tail(&node->nl_entry, &mm->nodes);
         list_add_tail(&node->fl_entry, &mm->free);
         mm->heap_nodes++;
-        mm->heap_size += length;
         return 0;
 }
 
diff --git a/drivers/gpu/drm/nouveau/core/include/core/mm.h b/drivers/gpu/drm/nouveau/core/include/core/mm.h
index 9ee9bf4028ca..975137ba34a6 100644
--- a/drivers/gpu/drm/nouveau/core/include/core/mm.h
+++ b/drivers/gpu/drm/nouveau/core/include/core/mm.h
@@ -19,7 +19,6 @@ struct nouveau_mm {
 
         u32 block_size;
         int heap_nodes;
-        u32 heap_size;
 };
 
 int  nouveau_mm_init(struct nouveau_mm *, u32 offset, u32 length, u32 block);