net: calxedaxgmac: fix rx ring handling when OOM

If skb allocation for the rx ring fails repeatedly, we can reach a point
were the ring is empty. In this condition, the driver is out of sync with
the h/w. While this has always been possible, the removal of the skb
recycling seems to have made triggering this problem easier.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c
index a170065..bb1e80b 100644 (file)
--- a/drivers/net/ethernet/calxeda/xgmac.c
+++ b/drivers/net/ethernet/calxeda/xgmac.c
@@ -1141,6 +1141,9 @@ static int xgmac_rx(struct xgmac_priv *priv, int limit)
                struct sk_buff *skb;
                int frame_len;
 
+               if (!dma_ring_cnt(priv->rx_head, priv->rx_tail, DMA_RX_RING_SZ))
+                       break;
+
                entry = priv->rx_tail;
                p = priv->dma_rx + entry;
                if (desc_get_owner(p))