net: calxedaxgmac: update ring buffer tx_head after barriers

Ensure that the descriptor writes are visible before the ring buffer head
is updated. Since writel is a barrier, we can simply update the head after
the writel.

Reported-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c
index 64854ad84b55..f63085571241 100644
--- a/drivers/net/ethernet/calxeda/xgmac.c
+++ b/drivers/net/ethernet/calxeda/xgmac.c
@@ -1121,9 +1121,10 @@ static netdev_tx_t xgmac_xmit(struct sk_buff *skb, struct net_device *dev)
         wmb();
         desc_set_tx_owner(first, desc_flags | TXDESC_FIRST_SEG);
 
+        writel(1, priv->base + XGMAC_DMA_TX_POLL);
+
         priv->tx_head = dma_ring_incr(entry, DMA_TX_RING_SZ);
 
-        writel(1, priv->base + XGMAC_DMA_TX_POLL);
         if (dma_ring_space(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ) <
             MAX_SKB_FRAGS)
                 netif_stop_queue(dev);