[PATCH v3 net-next] net/mlx5e: Report rx_discards_phy via rx_fifo_errors

[Yafang Shao <laoar.shao@gmail.com>]

We observed a high number of rx_discards_phy events on some servers when
running `ethtool -S`. However, this important counter is not currently
reflected in the /proc/net/dev statistics file, making it challenging to
monitor effectively.

Since rx_fifo_errors represents receive FIFO errors on this network
deivice, it makes sense to include rx_discards_phy in this counter to
enhance monitoring visibility. This change will help administrators track
these events more effectively through standard interfaces.

I have also verified the manual of ethtool counters on mlx5 [0], it seems
that rx_discards_phy and rx_fifo_errors has the same meaning:

  rx_discards_phy: The number of received packets 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.

                   ConnectX-3 naming : rx_fifo_errors

Link: https://enterprise-support.nvidia.com/s/article/understanding-mlx5-ethtool-counters [0]
Suggested-by: Tariq Toukan <ttoukan.linux@gmail.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Tariq Toukan <ttoukan.linux@gmail.com>
Cc: Saeed Mahameed <saeedm@nvidia.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Gal Pressman <gal@nvidia.com>
Cc: Jakub Kicinski <kuba@kernel.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 1 +
 1 file changed, 1 insertion(+)

Changes:
v2->v3:
- Drop the changes on the Doc

v1->v2: https://lore.kernel.org/netdev/20241114021711.5691-1-laoar.shao@gmail.com/
- Use rx_fifo_errors instead (Tariq)
- Update the if_link.h accordingly

v1: https://lore.kernel.org/netdev/20241106064015.4118-1-laoar.shao@gmail.com/

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index e601324a690a..15b1a3e6e641 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -3916,6 +3916,7 @@ mlx5e_get_stats(struct net_device *dev, struct rtnl_link_stats64 *stats)
 	}
 
 	stats->rx_missed_errors = priv->stats.qcnt.rx_out_of_buffer;
+	stats->rx_fifo_errors = PPORT_2863_GET(pstats, if_in_discards);
 
 	stats->rx_length_errors =
 		PPORT_802_3_GET(pstats, a_in_range_length_errors) +
-- 
2.43.5