[PATCH RFC 28/30] net: fec: add support for dumping transmit ring on timeout

[Russell King]

When we timeout on transmit, it would be useful to dump the transmit
ring, so we can see the ring state.  This can be helpful to diagnose
the cause of transmit timeouts.

Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
---
 drivers/net/ethernet/freescale/fec_main.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index c05f33896002..e170bea2f8cd 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -320,6 +320,27 @@ static void *swap_buffer(void *bufaddr, int len)
 	return bufaddr;
 }
 
+static void fec_dump(struct net_device *ndev)
+{
+	struct fec_enet_private *fep = netdev_priv(ndev);
+	struct bufdesc *bdp = fep->tx_bd_base;
+	unsigned int index = 0;
+
+	netdev_info(ndev, "TX ring dump\n");
+	pr_info("Nr     SC     addr       len  SKB\n");
+
+	do {
+		pr_info("%3u %c%c 0x%04x 0x%08lx %4u %p\n",
+			index,
+			bdp == fep->cur_tx ? 'S' : ' ',
+			bdp == fep->dirty_tx ? 'H' : ' ',
+			bdp->cbd_sc, bdp->cbd_bufaddr, bdp->cbd_datlen,
+			fep->tx_skbuff[index]);
+		bdp = fec_enet_get_nextdesc(bdp, fep);
+		index++;
+	} while (bdp != fep->tx_bd_base);
+}
+
 static inline bool is_ipv4_pkt(struct sk_buff *skb)
 {
 	return skb->protocol == htons(ETH_P_IP) && ip_hdr(skb)->version == 4;
@@ -1018,6 +1039,8 @@ fec_timeout(struct net_device *ndev)
 {
 	struct fec_enet_private *fep = netdev_priv(ndev);
 
+	fec_dump(ndev);
+
 	ndev->stats.tx_errors++;
 
 	schedule_work(&fep->tx_timeout_work);
-- 
1.8.3.1