net/mlx5e: Add discard counters per priority

Add counters that count (per priority) the number of received
packets that dropped due to lack of buffers on a physical port. If
this counter is increasing, it implies that the adapter is
congested and cannot absorb the traffic coming from the network.
Signed-off-by: Aharon Landau <aharonl@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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

@@ -1130,6 +1130,7 @@ static void mlx5e_grp_per_port_buffer_congest_update_stats(struct mlx5e_priv *pr
 static const struct counter_desc pport_per_prio_traffic_stats_desc[] = {
 	{ "rx_prio%d_bytes", PPORT_PER_PRIO_OFF(rx_octets) },
 	{ "rx_prio%d_packets", PPORT_PER_PRIO_OFF(rx_frames) },
+	{ "rx_prio%d_discards", PPORT_PER_PRIO_OFF(rx_discards) },
 	{ "tx_prio%d_bytes", PPORT_PER_PRIO_OFF(tx_octets) },
 	{ "tx_prio%d_packets", PPORT_PER_PRIO_OFF(tx_frames) },
 };

include/linux/mlx5/mlx5_ifc.h

@@ -2180,7 +2180,9 @@ struct mlx5_ifc_eth_per_prio_grp_data_layout_bits {
 
 	u8         rx_pause_transition_low[0x20];
 
-	u8         reserved_at_3c0[0x40];
+	u8         rx_discards_high[0x20];
+
+	u8         rx_discards_low[0x20];
 
 	u8         device_stall_minor_watermark_cnt_high[0x20];