WAN: Fix a TX IRQ causing BUG() in PC300 and PCI200SYN drivers.

We must not wake the TX queue without free TX descriptors.
sca_xmit() expects at least one free descriptor and BUGs otherwise.

Problem reported and fix tested by Bernie Innocenti and Ward Vandewege.

Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/net/wan/hd64572.c b/drivers/net/wan/hd64572.c
index ea476cbd38b5..e305274f83fb 100644
--- a/drivers/net/wan/hd64572.c
+++ b/drivers/net/wan/hd64572.c
@@ -293,6 +293,7 @@ static inline void sca_tx_done(port_t *port)
         struct net_device *dev = port->netdev;
         card_t* card = port->card;
         u8 stat;
+        unsigned count = 0;
 
         spin_lock(&port->lock);
 
@@ -316,10 +317,12 @@ static inline void sca_tx_done(port_t *port)
                         dev->stats.tx_bytes += readw(&desc->len);
                 }
                 writeb(0, &desc->stat); /* Free descriptor */
+                count++;
                 port->txlast = (port->txlast + 1) % card->tx_ring_buffers;
         }
 
-        netif_wake_queue(dev);
+        if (count)
+                netif_wake_queue(dev);
         spin_unlock(&port->lock);
 }