[PATCH 3.8 117/166] dm9601: work around tx fifo sync issue on dm962x

Kamal Mostafa
2014-01-15T21:52:11Z

From: Peter Korsgaard <peter@korsgaard.com>

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@davicom.com.tw>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@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 ae2668e..d3891b1 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