Commit 7d66c74a authored by Oleksij Rempel's avatar Oleksij Rempel Committed by Paolo Abeni
Browse files

Documentation: networking: update PHY error counter diagnostics in twisted pair guide 



Replace generic instructions for monitoring error counters with a
procedure using the unified PHY statistics interface (`--all-groups`).

Signed-off-by: default avatarOleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 6167c0b6

Documentation/networking/diagnostic/twisted_pair_layer1_diagnostics.rst

+28 −11
Original line number Diff line number Diff line
@@ -713,17 +713,23 @@ driver supports reporting such events. 


- **Monitor Error Counters**:



  - While some NIC drivers and PHYs provide error counters, there is no unified

    set of PHY-specific counters across all hardware. Additionally, not all

    PHYs provide useful information related to errors like CRC errors, frame

    drops, or link flaps. Therefore, this step is dependent on the specific

    hardware and driver support.



  - **Next Steps**: Use `ethtool -S <interface>` to check if your driver

    provides useful error counters. In some cases, counters may provide

    information about errors like link flaps or physical layer problems (e.g.,

    excessive CRC errors), but results can vary significantly depending on the

    PHY.

  - Use `ethtool -S <interface> --all-groups` to retrieve standardized interface

    statistics if the driver supports the unified interface:



  - **Command:** `ethtool -S <interface> --all-groups`



  - **Example Output (if supported)**:



    .. code-block:: bash



      phydev-RxFrames: 100391

      phydev-RxErrors: 0

      phydev-TxFrames: 9

      phydev-TxErrors: 0



  - If the unified interface is not supported, use `ethtool -S <interface>` to

    retrieve MAC and PHY counters. Note that non-standardized PHY counter names

    vary by driver and must be interpreted accordingly:



  - **Command:** `ethtool -S <interface>`
@@ -740,6 +746,17 @@ driver supports reporting such events. 
    condition) or kernel log messages (e.g., link up/down events) to further

    diagnose the issue.



  - **Compare Counters**:



    - Compare the egress and ingress frame counts reported by the PHY and MAC.



    - A small difference may occur due to sampling rate differences between the

      MAC and PHY drivers, or if the PHY and MAC are not always fully

      synchronized in their UP or DOWN states.



    - Significant discrepancies indicate potential issues in the data path

      between the MAC and PHY.



When All Else Fails...

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