[PATCH v2 4/4] doc: add PTP IDPF documentation

[Bruce Richardson]

On Tue, Oct 28, 2025 at 02:07:58AM -0400, Soumyadeep Hore wrote:
> Updated the IDPF Documentation with PTP feature.
> 
> Signed-off-by: Soumyadeep Hore <soumyadeep.hore at intel.com>
> ---
>  doc/guides/nics/idpf.rst | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/doc/guides/nics/idpf.rst b/doc/guides/nics/idpf.rst
> index b99cc18188..e76632904b 100644
> --- a/doc/guides/nics/idpf.rst
> +++ b/doc/guides/nics/idpf.rst
> @@ -109,3 +109,19 @@ The paths are chosen based on 2 conditions:
>    A value "P" means the offload feature is not supported by vector path.
>    If any not supported features are used, idpf vector PMD is disabled
>    and the scalar paths are chosen.
> +
> +Time Synchronisation
> +~~~~~~~~~~~~~~~~~~~~
> +
> +The system operator can run a PTP (Precision Time Protocol) client application
> +to synchronise the time on the network card in ACC
> +(and optionally the time on the system) to the PTP master.
> +
> +IDPF PMD supports PTP client applications that use the DPDK IEEE 1588 API
> +to communicate with the PTP master clock.
> +Note that PTP client application needs to run on PF in ACC
> +and add the ``--force-max-simd-bitwidth=64`` startup parameter to disable vector mode.
> +
> +.. code-block:: console
> +
> +   examples/dpdk-ptpclient -l 0-3 -n 3 -a 0000:ec:00.1 --force-max-simd-bitwidth=64 -- -T 1 -p 0x1 -c 1

Why is force-max-simd-bitwidth necessary? When using a feature not
supported by the vector driver path, the driver itself must be the one
which selects a scalar path. That task cannot fall to the user, or require
the user to know that he needs to select a scalar path.

/Bruce

> -- 
> 2.47.1
>