Report device_stall_critical_watermark_cnt as tx_pause_storm_events in
the ethtool_pause_stats struct. This counter tracks pause storm error
events which indicate the NIC has been sending pause frames for an
extended period due to a stall.

The ethtool_pause_stats struct reports these stalls as a single value,
whereas the device supports tracking them per priority. Aggregate the
counter across all priority classes to capture stalls on all priorities.
Note that the stats are fetched from the device for each priority via
mlx5_core_access_reg().

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
---
 .../ethernet/mellanox/mlx5/core/en_stats.c    | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c b/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
index a8af84fc9763..1a3ecf073913 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
@@ -916,11 +916,30 @@ static int mlx5e_stats_get_ieee(struct mlx5_core_dev *mdev,
 				    sz, MLX5_REG_PPCNT, 0, 0);
 }
 
+static int mlx5e_stats_get_per_prio(struct mlx5_core_dev *mdev,
+				    u32 *ppcnt_per_prio, int prio)
+{
+	u32 in[MLX5_ST_SZ_DW(ppcnt_reg)] = {};
+	int sz = MLX5_ST_SZ_BYTES(ppcnt_reg);
+
+	if (!(MLX5_CAP_PCAM_FEATURE(mdev, pfcc_mask) &&
+	      MLX5_CAP_DEBUG(mdev, stall_detect)))
+		return -EOPNOTSUPP;
+
+	MLX5_SET(ppcnt_reg, in, local_port, 1);
+	MLX5_SET(ppcnt_reg, in, grp, MLX5_PER_PRIORITY_COUNTERS_GROUP);
+	MLX5_SET(ppcnt_reg, in, prio_tc, prio);
+	return mlx5_core_access_reg(mdev, in, sz, ppcnt_per_prio, sz,
+				    MLX5_REG_PPCNT, 0, 0);
+}
+
 void mlx5e_stats_pause_get(struct mlx5e_priv *priv,
 			   struct ethtool_pause_stats *pause_stats)
 {
 	u32 ppcnt_ieee_802_3[MLX5_ST_SZ_DW(ppcnt_reg)];
 	struct mlx5_core_dev *mdev = priv->mdev;
+	u64 ps_stats = 0;
+	int prio;
 
 	if (mlx5e_stats_get_ieee(mdev, ppcnt_ieee_802_3))
 		return;
@@ -933,6 +952,17 @@ void mlx5e_stats_pause_get(struct mlx5e_priv *priv,
 		MLX5E_READ_CTR64_BE_F(ppcnt_ieee_802_3,
 				      eth_802_3_cntrs_grp_data_layout,
 				      a_pause_mac_ctrl_frames_received);
+
+	for (prio = 0; prio < NUM_PPORT_PRIO; prio++) {
+		if (mlx5e_stats_get_per_prio(mdev, ppcnt_ieee_802_3, prio))
+			return;
+
+		ps_stats += MLX5E_READ_CTR64_BE_F(ppcnt_ieee_802_3,
+						  eth_per_prio_grp_data_layout,
+						  device_stall_critical_watermark_cnt);
+	}
+
+	pause_stats->tx_pause_storm_events = ps_stats;
 }
 
 void mlx5e_stats_eth_phy_get(struct mlx5e_priv *priv,
-- 
2.47.3