[PATCH 3.2 093/115] net: dp83640: Fix tx timestamp overflow handling.

[Ben Hutchings]

3.2.80-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Manfred Rudigier <Manfred.Rudigier@xxxxxxxxxx>

[ Upstream commit 81e8f2e930fe76b9814c71b9d87c30760b5eb705 ]

PHY status frames are not reliable, the PHY may not be able to send them
during heavy receive traffic. This overflow condition is signaled by the
PHY in the next status frame, but the driver did not make use of it.
Instead it always reported wrong tx timestamps to user space after an
overflow happened because it assigned newly received tx timestamps to old
packets in the queue.

This commit fixes this issue by clearing the tx timestamp queue every time
an overflow happens, so that no timestamps are delivered for overflow
packets. This way time stamping will continue correctly after an overflow.

Signed-off-by: Manfred Rudigier <manfred.rudigier@xxxxxxxxxx>
Acked-by: Richard Cochran <richardcochran@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/net/phy/dp83640.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

--- a/drivers/net/phy/dp83640.c
+++ b/drivers/net/phy/dp83640.c
@@ -680,6 +680,11 @@ static void decode_rxts(struct dp83640_p
 {
 	struct rxts *rxts;
 	unsigned long flags;
+	u8 overflow;
+
+	overflow = (phy_rxts->ns_hi >> 14) & 0x3;
+	if (overflow)
+		pr_debug("rx timestamp queue overflow, count %d\n", overflow);
 
 	spin_lock_irqsave(&dp83640->rx_lock, flags);
 
@@ -703,6 +708,7 @@ static void decode_txts(struct dp83640_p
 	struct skb_shared_hwtstamps shhwtstamps;
 	struct sk_buff *skb;
 	u64 ns;
+	u8 overflow;
 
 	/* We must already have the skb that triggered this. */
 
@@ -712,6 +718,17 @@ static void decode_txts(struct dp83640_p
 		pr_debug("dp83640: have timestamp but tx_queue empty\n");
 		return;
 	}
+
+	overflow = (phy_txts->ns_hi >> 14) & 0x3;
+	if (overflow) {
+		pr_debug("tx timestamp queue overflow, count %d\n", overflow);
+		while (skb) {
+			skb_complete_tx_timestamp(skb, NULL);
+			skb = skb_dequeue(&dp83640->tx_queue);
+		}
+		return;
+	}
+
 	ns = phy2txts(phy_txts);
 	memset(&shhwtstamps, 0, sizeof(shhwtstamps));
 	shhwtstamps.hwtstamp = ns_to_ktime(ns);