net: nps_enet: bug fix - handle lost tx interrupts

The tx interrupt is of edge type, and in case such interrupt is triggered
while it is masked it will not be handled even after tx interrupts are
re-enabled in the end of NAPI poll.
This will cause tx network to stop in the following scenario:
 * Rx is being handled, hence interrupts are masked.
 * Tx interrupt is triggered after checking if there is some tx to handle
   and before re-enabling the interrupts.
In this situation only rx transaction will release tx requests.

In order to handle the tx that was missed( if there was one ),
a NAPI reschdule was added after enabling the interrupts.

Signed-off-by: Elad Kanfi <eladkan@mellanox.com>
Acked-by: Noam Camus <noamca@mellanox.com>
Acked-by: Gilad Ben-Yossef <giladby@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ezchip/nps_enet.c

@@ -183,6 +183,9 @@ static int nps_enet_poll(struct napi_struct *napi, int budget)
 	work_done = nps_enet_rx_handler(ndev);
 	if (work_done < budget) {
 		u32 buf_int_enable_value = 0;
+		u32 tx_ctrl_value = nps_enet_reg_get(priv, NPS_ENET_REG_TX_CTL);
+		u32 tx_ctrl_ct =
+			(tx_ctrl_value & TX_CTL_CT_MASK) >> TX_CTL_CT_SHIFT;
 
 		napi_complete(napi);
 
@@ -192,6 +195,18 @@ static int nps_enet_poll(struct napi_struct *napi, int budget)
 
 		nps_enet_reg_set(priv, NPS_ENET_REG_BUF_INT_ENABLE,
 				 buf_int_enable_value);
+
+		/* in case we will get a tx interrupt while interrupts
+		 * are masked, we will lose it since the tx is edge interrupt.
+		 * specifically, while executing the code section above,
+		 * between nps_enet_tx_handler and the interrupts enable, all
+		 * tx requests will be stuck until we will get an rx interrupt.
+		 * the two code lines below will solve this situation by
+		 * re-adding ourselves to the poll list.
+		 */
+
+		if (priv->tx_skb && !tx_ctrl_ct)
+			napi_reschedule(napi);
 	}
 
 	return work_done;