net: ethernet: cpsw: fix usage of cpdma_check_free_tx_desc()

Commit fae5082 ("net: ethernet: davinci_cpdma: Add boundary for rx
and tx descriptors") introduced a function to check the current
allocation state of tx packets. The return value is taken into account
to stop the netqork queue on the adapter in case there are no free
slots.

However, cpdma_check_free_tx_desc() returns 'true' if there is room in
the bitmap, not 'false', so the usage of the function is wrong.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: Mugunthan V N <mugunthanvnm@ti.com>
Reported-by: Sven Neumann <s.neumann@raumfeld.com>
Reported-by: Andreas Fenkart <andreas.fenkart@streamunlimited.com>
Tested-by: Mugunthan V N <mugunthanvnm@ti.com>
Acked-by: Mugunthan V N <mugunthanvnm@ti.com>
Tested-by: Andreas Fenkart <andreas.fenkart@streamunlimited.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/cpsw.c

@@ -905,7 +905,7 @@ static netdev_tx_t cpsw_ndo_start_xmit(struct sk_buff *skb,
 	/* If there is no more tx desc left free then we need to
 	 * tell the kernel to stop sending us tx frames.
 	 */
-	if (unlikely(cpdma_check_free_tx_desc(priv->txch)))
+	if (unlikely(!cpdma_check_free_tx_desc(priv->txch)))
 		netif_stop_queue(ndev);
 
 	return NETDEV_TX_OK;