[PATCH 4.0 068/148] staging: vt6655: vnt_tx_packet Correct TX order of OWNED_BY_NIC

Greg Kroah-Hartman
2015-06-03T12:20:50Z

From: Malcolm Priestley <tvboxspy@gmail.com>

commit d65d2b25d2761153390df8026cca1a528d9b6c5a upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/vt6655/device_main.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

--- a/drivers/staging/vt6655/device_main.c
+++ b/drivers/staging/vt6655/device_main.c
@@ -1203,14 +1203,6 @@ static int vnt_tx_packet(struct vnt_priv
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);
@@ -1231,11 +1223,18 @@ static int vnt_tx_packet(struct vnt_priv

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;