net/mlx5e: Introduce timestamps statistic counter for Tx DMA layer

Count number of transmitted packets that were hardware timestamped at the
device DMA layer.
Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Link: https://lore.kernel.org/r/20240403212931.128541-4-rrameshbabu@nvidia.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/device_drivers/ethernet/mellanox/mlx5/counters.rst

@@ -300,6 +300,11 @@ the software port.
        in the beginning of the queue. This is a normal condition.
      - Informative
 
+   * - `tx[i]_timestamps`
+     - Transmitted packets that were hardware timestamped at the device's DMA
+       layer.
+     - Informative
+
    * - `tx[i]_added_vlan_packets`
      - The number of packets sent where vlan tag insertion was offloaded to the
        hardware.

drivers/net/ethernet/mellanox/mlx5/core/en_stats.c

@@ -2066,6 +2066,7 @@ static const struct counter_desc sq_stats_desc[] = {
 	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, csum_partial_inner) },
 	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, added_vlan_packets) },
 	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, nop) },
+	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, timestamps) },
 	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, mpwqe_blks) },
 	{ MLX5E_DECLARE_TX_STAT(struct mlx5e_sq_stats, mpwqe_pkts) },
 #ifdef CONFIG_MLX5_EN_TLS
@@ -2218,6 +2219,7 @@ static const struct counter_desc qos_sq_stats_desc[] = {
 	{ MLX5E_DECLARE_QOS_TX_STAT(struct mlx5e_sq_stats, csum_partial_inner) },
 	{ MLX5E_DECLARE_QOS_TX_STAT(struct mlx5e_sq_stats, added_vlan_packets) },
 	{ MLX5E_DECLARE_QOS_TX_STAT(struct mlx5e_sq_stats, nop) },
+	{ MLX5E_DECLARE_QOS_TX_STAT(struct mlx5e_sq_stats, timestamps) },
 	{ MLX5E_DECLARE_QOS_TX_STAT(struct mlx5e_sq_stats, mpwqe_blks) },
 	{ MLX5E_DECLARE_QOS_TX_STAT(struct mlx5e_sq_stats, mpwqe_pkts) },
 #ifdef CONFIG_MLX5_EN_TLS

drivers/net/ethernet/mellanox/mlx5/core/en_stats.h

@@ -431,6 +431,7 @@ struct mlx5e_sq_stats {
 	u64 stopped;
 	u64 dropped;
 	u64 recover;
+	u64 timestamps;
 	/* dirtied @completion */
 	u64 cqes ____cacheline_aligned_in_smp;
 	u64 wake;

drivers/net/ethernet/mellanox/mlx5/core/en_tx.c

@@ -750,11 +750,13 @@ static void mlx5e_consume_skb(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 		u64 ts = get_cqe_ts(cqe);
 
 		hwts.hwtstamp = mlx5e_cqe_ts_to_ns(sq->ptp_cyc2time, sq->clock, ts);
-		if (sq->ptpsq)
+		if (sq->ptpsq) {
 			mlx5e_skb_cb_hwtstamp_handler(skb, MLX5E_SKB_CB_CQE_HWTSTAMP,
 						      hwts.hwtstamp, sq->ptpsq->cq_stats);
-		else
+		} else {
 			skb_tstamp_tx(skb, &hwts);
+			sq->stats->timestamps++;
+		}
 	}
 
 	napi_consume_skb(skb, napi_budget);