[3.11.y.z extended stable] Patch "dm9601: work around tx fifo sync issue on dm962x" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    dm9601: work around tx fifo sync issue on dm962x

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 9163a1bfbbe79b5a4703f9dde0337e7d07d9b006 Mon Sep 17 00:00:00 2001
From: Peter Korsgaard <peter at korsgaard.com>
Date: Mon, 16 Dec 2013 11:35:35 +0100
Subject: dm9601: work around tx fifo sync issue on dm962x

commit 4263c86dca5198da6bd3ad826d0b2304fbe25776 upstream.

Certain dm962x revisions contain an bug, where if a USB bulk transfer retry
(E.G. if bulk crc mismatch) happens right after a transfer with odd or
maxpacket length, the internal tx hardware fifo gets out of sync causing
the interface to stop working.

Work around it by adding up to 3 bytes of padding to ensure this situation
cannot trigger.

This workaround also means we never pass multiple-of-maxpacket size skb's
to usbnet, so the length adjustment to handle usbnet's padding of those can
be removed.

Reported-by: Joseph Chang <joseph_chang at davicom.com.tw>
Signed-off-by: Peter Korsgaard <peter at korsgaard.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/usb/dm9601.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/net/usb/dm9601.c b/drivers/net/usb/dm9601.c
index 732a926..c0bfc81 100644
--- a/drivers/net/usb/dm9601.c
+++ b/drivers/net/usb/dm9601.c
@@ -473,7 +473,7 @@ static int dm9601_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 static struct sk_buff *dm9601_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 				       gfp_t flags)
 {
-	int len;
+	int len, pad;

 	/* format:
 	   b1: packet length low
@@ -481,12 +481,23 @@ static struct sk_buff *dm9601_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 	   b3..n: packet data
 	*/

-	len = skb->len;
+	len = skb->len + DM_TX_OVERHEAD;
+
+	/* workaround for dm962x errata with tx fifo getting out of
+	 * sync if a USB bulk transfer retry happens right after a
+	 * packet with odd / maxpacket length by adding up to 3 bytes
+	 * padding.
+	 */
+	while ((len & 1) || !(len % dev->maxpacket))
+		len++;

-	if (skb_headroom(skb) < DM_TX_OVERHEAD) {
+	len -= DM_TX_OVERHEAD; /* hw header doesn't count as part of length */
+	pad = len - skb->len;
+
+	if (skb_headroom(skb) < DM_TX_OVERHEAD || skb_tailroom(skb) < pad) {
 		struct sk_buff *skb2;

-		skb2 = skb_copy_expand(skb, DM_TX_OVERHEAD, 0, flags);
+		skb2 = skb_copy_expand(skb, DM_TX_OVERHEAD, pad, flags);
 		dev_kfree_skb_any(skb);
 		skb = skb2;
 		if (!skb)
@@ -495,10 +506,10 @@ static struct sk_buff *dm9601_tx_fixup(struct usbnet *dev, struct sk_buff *skb,

 	__skb_push(skb, DM_TX_OVERHEAD);

-	/* usbnet adds padding if length is a multiple of packet size
-	   if so, adjust length value in header */
-	if ((skb->len % dev->maxpacket) == 0)
-		len++;
+	if (pad) {
+		memset(skb->data + skb->len, 0, pad);
+		__skb_put(skb, pad);
+	}

 	skb->data[0] = len;
 	skb->data[1] = len >> 8;
--
1.8.3.2