[PATCH net v2 3/4] net: macb: increment stats.tx_dropped on tx error

["Théo Lebrun" <theo.lebrun@bootlin.com>]

macb_tx_error_task() is the workqueue callback on Tx errors interrupts
(MACB_TX_ERR_FLAGS). Count number of errored SKBs and increment the Tx
dropped stat by that amount.

Two types of dropped (not consumed) packets:
 - Those that have been TX_USED but with an error.
 - Those that have not been TX_USED but that'll we drop to reset.

Fixes: 89e5785fc8a6 ("[PATCH] Atmel MACB ethernet driver")
Cc: stable@vger.kernel.org
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 5a2500bd59a6..ba7cbb10dc2c 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -1261,6 +1261,7 @@ static void macb_tx_error_task(struct work_struct *work)
 	struct macb		*bp = queue->bp;
 	u32			queue_index;
 	u32			packets = 0;
+	unsigned int		dropped = 0;
 	u32			bytes = 0;
 	struct macb_tx_skb	*tx_skb;
 	struct macb_dma_desc	*desc;
@@ -1332,6 +1333,8 @@ static void macb_tx_error_task(struct work_struct *work)
 				queue->stats.tx_bytes += skb->len;
 				bytes += skb->len;
 				reason = SKB_CONSUMED;
+			} else {
+				dropped++;
 			}
 		} else {
 			/* "Buffers exhausted mid-frame" errors may only happen
@@ -1343,11 +1346,17 @@ static void macb_tx_error_task(struct work_struct *work)
 					   "BUG: TX buffers exhausted mid-frame\n");
 
 			desc->ctrl = ctrl | MACB_BIT(TX_USED);
+
+			if (skb)
+				dropped++;
 		}
 
 		macb_tx_unmap(bp, tx_skb, 0, reason);
 	}
 
+	queue->stats.tx_dropped += dropped;
+	bp->dev->stats.tx_dropped += dropped;
+
 	netdev_tx_completed_queue(netdev_get_tx_queue(bp->dev, queue_index),
 				  packets, bytes);
 

-- 
2.54.0