[PATCH V3 net 3/3] net: ena: Make missed_tx stat incremental

[Shay Agroskin <shayagr@amazon.com>]

Most statistics in ena driver are incremented, meaning that a stat's
value is a sum of all increases done to it since driver/queue
initialization.

This patch makes all statistics this way, effectively making missed_tx
statistic incremental.
Also added a comment regarding rx_drops and tx_drops to make it
clearer how these counters are calculated.

Fixes: 11095fdb712b ("net: ena: add statistics for missed tx packets")
Signed-off-by: Shay Agroskin <shayagr@amazon.com>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 233db15c970d..a3a8edf9a734 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -3687,7 +3687,7 @@ static int check_missing_comp_in_tx_queue(struct ena_adapter *adapter,
 	}
 
 	u64_stats_update_begin(&tx_ring->syncp);
-	tx_ring->tx_stats.missed_tx = missed_tx;
+	tx_ring->tx_stats.missed_tx += missed_tx;
 	u64_stats_update_end(&tx_ring->syncp);
 
 	return rc;
@@ -4556,6 +4556,9 @@ static void ena_keep_alive_wd(void *adapter_data,
 	tx_drops = ((u64)desc->tx_drops_high << 32) | desc->tx_drops_low;
 
 	u64_stats_update_begin(&adapter->syncp);
+	/* These stats are accumulated by the device, so the counters indicate
+	 * all drops since last reset.
+	 */
 	adapter->dev_stats.rx_drops = rx_drops;
 	adapter->dev_stats.tx_drops = tx_drops;
 	u64_stats_update_end(&adapter->syncp);
-- 
2.17.1