mlxsw: spectrum_qdisc: Introduce per-TC ECN counters

The Qdisc code in mlxsw used to report a number of packets ECN-marked on a
port. Because reporting a per-port value as a per-TC value was misleading,
this was removed in commit 8a29581 ("mlxsw: spectrum: Move the
ECN-marked packet counter to ethtool").

On Spectrum-3, a per-TC number of ECN-marked packets is available in per-TC
congestion counter group. Add a new array for the ECN counter, fetch the
values from the per-TC congestion group, and pick the value indicated by
tclass_num as appropriate.

On Spectrum-1 and Spectrum-2, this per-TC value is not available, and
zeroes will be reported, as they currently are.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -826,10 +826,14 @@ mlxsw_sp_port_get_hw_xstats(struct net_device *dev,
 		err = mlxsw_sp_port_get_stats_raw(dev,
 						  MLXSW_REG_PPCNT_TC_CONG_CNT,
 						  i, ppcnt_pl);
-		if (!err)
-			xstats->wred_drop[i] =
-				mlxsw_reg_ppcnt_wred_discard_get(ppcnt_pl);
+		if (err)
+			goto tc_cnt;
+
+		xstats->wred_drop[i] =
+			mlxsw_reg_ppcnt_wred_discard_get(ppcnt_pl);
+		xstats->tc_ecn[i] = mlxsw_reg_ppcnt_ecn_marked_tc_get(ppcnt_pl);
 
+tc_cnt:
 		err = mlxsw_sp_port_get_stats_raw(dev, MLXSW_REG_PPCNT_TC_CNT,
 						  i, ppcnt_pl);
 		if (err)

drivers/net/ethernet/mellanox/mlxsw/spectrum.h

@@ -285,6 +285,7 @@ struct mlxsw_sp_port_vlan {
 /* No need an internal lock; At worse - miss a single periodic iteration */
 struct mlxsw_sp_port_xstats {
 	u64 ecn;
+	u64 tc_ecn[TC_MAX_QUEUE];
 	u64 wred_drop[TC_MAX_QUEUE];
 	u64 tail_drop[TC_MAX_QUEUE];
 	u64 backlog[TC_MAX_QUEUE];

drivers/net/ethernet/mellanox/mlxsw/spectrum_qdisc.c

@@ -519,6 +519,7 @@ mlxsw_sp_setup_tc_qdisc_red_clean_stats(struct mlxsw_sp_port *mlxsw_sp_port,
 					       mlxsw_sp_qdisc->prio_bitmap,
 					       &stats_base->tx_packets,
 					       &stats_base->tx_bytes);
+	red_base->prob_mark = xstats->tc_ecn[tclass_num];
 	red_base->prob_drop = xstats->wred_drop[tclass_num];
 	red_base->pdrop = mlxsw_sp_xstats_tail_drop(xstats, tclass_num);
 
@@ -618,19 +619,22 @@ mlxsw_sp_qdisc_get_red_xstats(struct mlxsw_sp_port *mlxsw_sp_port,
 	int tclass_num = mlxsw_sp_qdisc->tclass_num;
 	struct mlxsw_sp_port_xstats *xstats;
 	struct red_stats *res = xstats_ptr;
-	int early_drops, pdrops;
+	int early_drops, marks, pdrops;
 
 	xstats = &mlxsw_sp_port->periodic_hw_stats.xstats;
 
 	early_drops = xstats->wred_drop[tclass_num] - xstats_base->prob_drop;
+	marks = xstats->tc_ecn[tclass_num] - xstats_base->prob_mark;
 	pdrops = mlxsw_sp_xstats_tail_drop(xstats, tclass_num) -
 		 xstats_base->pdrop;
 
 	res->pdrop += pdrops;
 	res->prob_drop += early_drops;
+	res->prob_mark += marks;
 
 	xstats_base->pdrop += pdrops;
 	xstats_base->prob_drop += early_drops;
+	xstats_base->prob_mark += marks;
 	return 0;
 }
 
@@ -648,7 +652,8 @@ mlxsw_sp_qdisc_get_red_stats(struct mlxsw_sp_port *mlxsw_sp_port,
 	stats_base = &mlxsw_sp_qdisc->stats_base;
 
 	mlxsw_sp_qdisc_get_tc_stats(mlxsw_sp_port, mlxsw_sp_qdisc, stats_ptr);
-	overlimits = xstats->wred_drop[tclass_num] - stats_base->overlimits;
+	overlimits = xstats->wred_drop[tclass_num] +
+		     xstats->tc_ecn[tclass_num] - stats_base->overlimits;
 
 	stats_ptr->qstats->overlimits += overlimits;
 	stats_base->overlimits += overlimits;