staging: vt6655: vnt_tx_packet Correct TX order of OWNED_BY_NIC

The state of m_td0TD0.f1Owner should change after the buff_addr
has been filled otherwise the device grabs the buffer too early.

m_td0TD0.f1Owner is protected by memory barriers on both sides
of change.

iTDUsed is best incremented after MACvTransmit.

It appears that f1Owner actually polls to do the memory transfer.

A back port patch will be needed for v3.19

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Cc: <stable@vger.kernel.org> # v4.0+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/vt6655/device_main.c b/drivers/staging/vt6655/device_main.c
index c817763..930bbbe 100644 (file)
--- a/drivers/staging/vt6655/device_main.c
+++ b/drivers/staging/vt6655/device_main.c
@@ -1206,14 +1206,6 @@ static int vnt_tx_packet(struct vnt_private *priv, struct sk_buff *skb)
        if (dma_idx == TYPE_AC0DMA)
                head_td->pTDInfo->byFlags = TD_FLAGS_NETIF_SKB;
 
-       priv->iTDUsed[dma_idx]++;
-
-       /* Take ownership */
-       wmb();
-       head_td->m_td0TD0.f1Owner = OWNED_BY_NIC;
-
-       /* get Next */
-       wmb();
        priv->apCurrTD[dma_idx] = head_td->next;
 
        spin_unlock_irqrestore(&priv->lock, flags);
@@ -1234,11 +1226,18 @@ static int vnt_tx_packet(struct vnt_private *priv, struct sk_buff *skb)
 
        head_td->buff_addr = cpu_to_le32(head_td->pTDInfo->skb_dma);
 
+       /* Poll Transmit the adapter */
+       wmb();
+       head_td->m_td0TD0.f1Owner = OWNED_BY_NIC;
+       wmb(); /* second memory barrier */
+
        if (head_td->pTDInfo->byFlags & TD_FLAGS_NETIF_SKB)
                MACvTransmitAC0(priv->PortOffset);
        else
                MACvTransmit0(priv->PortOffset);
 
+       priv->iTDUsed[dma_idx]++;
+
        spin_unlock_irqrestore(&priv->lock, flags);
 
        return 0;