drm/nouveau: handle same-fb page flips

It's questionable use case, but weston/wayland already relies on this
behaviour, and other drivers don't care about it, so it's a matter of
compatibility.  Without it, process invoking such page flip hangs in
unkillable state, trying to reserve the same buffer twice.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
index 61f370d..53ee303 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_display.c
+++ b/drivers/gpu/drm/nouveau/nouveau_display.c
@@ -530,9 +530,11 @@ nouveau_page_flip_reserve(struct nouveau_bo *old_bo,
        if (ret)
                goto fail;
 
-       ret = ttm_bo_reserve(&old_bo->bo, false, false, false, 0);
-       if (ret)
-               goto fail_unreserve;
+       if (likely(old_bo != new_bo)) {
+               ret = ttm_bo_reserve(&old_bo->bo, false, false, false, 0);
+               if (ret)
+                       goto fail_unreserve;
+       }
 
        return 0;
 
@@ -551,8 +553,10 @@ nouveau_page_flip_unreserve(struct nouveau_bo *old_bo,
        nouveau_bo_fence(new_bo, fence);
        ttm_bo_unreserve(&new_bo->bo);
 
-       nouveau_bo_fence(old_bo, fence);
-       ttm_bo_unreserve(&old_bo->bo);
+       if (likely(old_bo != new_bo)) {
+               nouveau_bo_fence(old_bo, fence);
+               ttm_bo_unreserve(&old_bo->bo);
+       }
 
        nouveau_bo_unpin(old_bo);
 }