[PATCH] mlx4_en: fix transmit of packages when blue frame is enabled

[Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>]

With the addition of Blue Frame support in the network driver for mlx4,
the doorbell is not written in the path where blue frame is enabled and
the package follows some characteristics.

The consequence of that is that ICMP ECHO requests, for example, were
not transmitted by the device. A ping flood, for example, would make the
watchdog dispatch, because the ring was full and transmissions have
timed out.

After this fix, I could ping two systems using mlx4_en (both with the
fix).

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Cc: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
---
 drivers/net/ethernet/mellanox/mlx4/en_tx.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 6e03de0..270da80 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -811,10 +811,11 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		* before setting ownership of this descriptor to HW */
 		wmb();
 		tx_desc->ctrl.owner_opcode = op_own;
-		wmb();
-		writel(ring->doorbell_qpn, ring->bf.uar->map + MLX4_SEND_DOORBELL);
 	}
 
+	wmb();
+	writel(ring->doorbell_qpn, ring->bf.uar->map + MLX4_SEND_DOORBELL);
+
 	/* Poll CQ here */
 	mlx4_en_xmit_poll(priv, tx_ind);
 
-- 
1.7.4.4