net: macb: Reset TX when TX halt times out

Reset TX when halt times out i.e. disable TX, clean up TX BDs,
interrupts (already done) and enable TX.
This addresses the issue observed when iperf is run at 10Mps Half
duplex where, after multiple collisions and retries, TX halts.

Signed-off-by: Harini Katakam <harini.katakam@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -1070,6 +1070,7 @@ static void macb_tx_error_task(struct work_struct *work)
 {
 	struct macb_queue	*queue = container_of(work, struct macb_queue,
 						      tx_error_task);
+	bool			halt_timeout = false;
 	struct macb		*bp = queue->bp;
 	struct macb_tx_skb	*tx_skb;
 	struct macb_dma_desc	*desc;
@@ -1097,9 +1098,11 @@ static void macb_tx_error_task(struct work_struct *work)
 	 * (in case we have just queued new packets)
 	 * macb/gem must be halted to write TBQP register
 	 */
-	if (macb_halt_tx(bp))
-		/* Just complain for now, reinitializing TX path can be good */
+	if (macb_halt_tx(bp)) {
 		netdev_err(bp->dev, "BUG: halt tx timed out\n");
+		macb_writel(bp, NCR, macb_readl(bp, NCR) & (~MACB_BIT(TE)));
+		halt_timeout = true;
+	}
 
 	/* Treat frames in TX queue including the ones that caused the error.
 	 * Free transmit buffers in upper layer.
@@ -1170,6 +1173,9 @@ static void macb_tx_error_task(struct work_struct *work)
 	macb_writel(bp, TSR, macb_readl(bp, TSR));
 	queue_writel(queue, IER, MACB_TX_INT_FLAGS);
 
+	if (halt_timeout)
+		macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TE));
+
 	/* Now we are ready to start transmission again */
 	netif_tx_start_all_queues(bp->dev);
 	macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));