drm/nv50: prevent (IB_PUT == IB_GET) for occurring unless idle

Should fix a DMA race condition I've never seen myself, but could be
the culprit in some random hangs that have been reported.

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

diff --git a/drivers/gpu/drm/nouveau/nouveau_dma.c b/drivers/gpu/drm/nouveau/nouveau_dma.c
index 9d27acd..eb24e2b 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_dma.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dma.c
@@ -214,7 +214,7 @@ nv50_dma_push_wait(struct nouveau_channel *chan, int count)
 
                chan->dma.ib_free = get - chan->dma.ib_put;
                if (chan->dma.ib_free <= 0)
-                       chan->dma.ib_free += chan->dma.ib_max + 1;
+                       chan->dma.ib_free += chan->dma.ib_max;
        }
 
        return 0;