Patch "net: dp83640: Fix tx timestamp overflow handling." has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

net: dp83640: Fix tx timestamp overflow handling.

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-dp83640-fix-tx-timestamp-overflow-handling.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Manfred Rudigier <[email protected]>
Date: Wed, 20 Jan 2016 11:22:28 +0100
Subject: net: dp83640: Fix tx timestamp overflow handling.

From: Manfred Rudigier <[email protected]>

[ 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.

---
 drivers/net/phy/dp83640.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

@@ -845,6 +845,11 @@ static void decode_rxts(struct dp83640_p
 	struct skb_shared_hwtstamps *shhwtstamps = NULL;
 	struct sk_buff *skb;
 	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);
 

@@ -887,6 +892,7 @@ 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. */
 

@@ -896,6 +902,17 @@ static void decode_txts(struct dp83640_p
 		pr_debug("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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/net-dp83640-fix-tx-timestamp-overflow-handling.patch