I'm currently using the MV643xx Ethernet driver on my board. When I run
the command :
# ifconfig eth0 down
I see the following message :
eth0: Error on Tx descriptor free - could not free 1 descriptors
I went through the code, and saw that this message is displayed in
mv64340_eth_free_tx_rings(). This function frees all remaining skbs
(registered in the mp->tx_skb array), and decrement mp->tx_ring_skbs.
Then, it checks if it reached 0. In my case, it is still 1.
In fact, mp->tx_ring_skbs is initialized to 0 and then incremented in
mv64340_eth_start_xmit() (when a transmission starts), and is
decremented in mv64340_eth_free_tx_queue (when the transmission is
done). But the decrementation only occurs if mp->tx_ring_skbs is
different from one. I don't understand why.
At the end of mv64340_eth_free_tx_queue(), the following code makes sure
that the number of skbs did not reach 0 :
if (mp->tx_ring_skbs == 0)
panic("ERROR - TX outstanding SKBs counter is corrupted");
Well, my question is simply : why can't we decrement the
mp->tx_ring_skbs counter to 0 ?
What needs to be fixed ? The decrementation of the counter, or the
function that frees the TX queue when the interface is stopped ?
I've seen similar code in the Titan GE driver.
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