On 2026/01/13 15:43, Tariq Toukan wrote:

On 13/01/2026 8:31, Tariq Toukan wrote:

quoted

On 12/01/2026 9:03, Kenta Akagi wrote:

quoted

Hi,

I would like to measure the cable BER on ConnectX.

According to the documentation[1][2], there are counters that can be used
for this purpose: rx_corrected_bits_phy, rx_pcs_symbol_err_phy and
rx_bits_phy. However, rx_bits_phy does not show up in ethtool
statistics.

This patch exposes the PPCNT phy_received_bits as rx_bits_phy.


On a ConnectX-5 with 25Gbase connection, it works as expected.

On the other hand, although I have not verified it, in an 800Gbps
environment rx_bits_phy would likely overflow after about 124 days.
Since I cannot judge whether this is acceptable, I am posting this as an
RFC first.

Hi,

This is a 64-bits counter so no overflow is expected.

Sorry, ignore my comment, your numbers make sense.
Maybe it's ~248 days, but same idea.

Hi, thank you for checking.

Ah, it seems I didn't realize it was unsigned, and I also forgot to
include the expression. Sorry about that.
Yes - at 800 Gbps, 0xFFFFFFFFFFFFFFFF / (800 * (2^30) * 86400) = 248.55 days,
so it will overflow.

In practice, is it possible to expose this as a statistic via ethtool?
Or is there some other value that could be exposed for BER calculation - e.g.,
a register that indicates the elapsed seconds since link-up?

Thanks.

quoted

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[1] commit 8ce3b586faa4 ("net/mlx5: Add counter information to mlx5
     driver documentation")
[2] https://docs.kernel.org/networking/device_drivers/ethernet/ mellanox/mlx5/counters.html

Kenta Akagi (1):
   net/mlx5e: Expose physical received bits counters to ethtool

  drivers/net/ethernet/mellanox/mlx5/core/en_stats.c | 1 +
  1 file changed, 1 insertion(+)