linux-kernel - [PATCH 4.0 068/148] staging: vt6655: vnt_tx_packet Correct TX order of OWNED_BY

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Message-Id: <20150603114208.339160901@linuxfoundation.org>
Date:	Wed,  3 Jun 2015 21:08:58 +0900
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Malcolm Priestley <tvboxspy@...il.com>
Subject: [PATCH 4.0 068/148] staging: vt6655: vnt_tx_packet Correct TX order of OWNED_BY_NIC

4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Malcolm Priestley <tvboxspy@...il.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@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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;


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