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>

1 files changed, 9 insertions, 5 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
index 61f370d000e..53ee3037d30 100644
--- 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);
 }