mlx4_en: fix endianness with blue frame support

The doorbell register was being unconditionally swapped. In x86, that
meant it was being swapped to BE and written to the descriptor and to
memory, depending on the case of blue frame support or writing to
doorbell register. On PPC, this meant it was being swapped to LE and
then swapped back to BE while writing to the register. But in the blue
frame case, it was being written as LE to the descriptor.

The fix is not to swap doorbell unconditionally, write it to the
register as BE and convert it to BE when writing it to the descriptor.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Reported-by: Richard Hendrickson <richhend@us.ibm.com>
Cc: Eli Cohen <eli@dev.mellanox.co.il>
Cc: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mlx4/en_tx.c

@@ -172,7 +172,7 @@ int mlx4_en_activate_tx_ring(struct mlx4_en_priv *priv,
 	memset(ring->buf, 0, ring->buf_size);
 
 	ring->qp_state = MLX4_QP_STATE_RST;
-	ring->doorbell_qpn = swab32(ring->qp.qpn << 8);
+	ring->doorbell_qpn = ring->qp.qpn << 8;
 
 	mlx4_en_fill_qp_context(priv, ring->size, ring->stride, 1, 0, ring->qpn,
 				ring->cqn, &ring->context);
@@ -791,7 +791,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		skb_orphan(skb);
 
 	if (ring->bf_enabled && desc_size <= MAX_BF && !bounce && !vlan_tag) {
-		*(u32 *) (&tx_desc->ctrl.vlan_tag) |= ring->doorbell_qpn;
+		*(__be32 *) (&tx_desc->ctrl.vlan_tag) |= cpu_to_be32(ring->doorbell_qpn);
 		op_own |= htonl((bf_index & 0xffff) << 8);
 		/* Ensure new descirptor hits memory
 		* before setting ownership of this descriptor to HW */
@@ -812,7 +812,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		wmb();
 		tx_desc->ctrl.owner_opcode = op_own;
 		wmb();
-		writel(ring->doorbell_qpn, ring->bf.uar->map + MLX4_SEND_DOORBELL);
+		iowrite32be(ring->doorbell_qpn, ring->bf.uar->map + MLX4_SEND_DOORBELL);
 	}
 
 	/* Poll CQ here */