RE: [PATCH v8 net-next 5/5] net: ena: Add PHC documentation

["Arinzon, David" <darinzon@amazon.com>]

> > +The feature is turned off by default, in order to turn the feature
> > +on, please use the following:
> > +
> > +- sysfs (during runtime):
> > +
> > +.. code-block:: shell
> > +
> > +  echo 1 > /sys/bus/pci/devices/<domain:bus:slot.function>/phc_enable
> > +
> > +All available PTP clock sources can be tracked here:
> > +
> > +.. code-block:: shell
> > +
> > +  ls /sys/class/ptp
> > +
> > +PHC support and capabilities can be verified using ethtool:
> > +
> > +.. code-block:: shell
> > +
> > +  ethtool -T <interface>
> > +
> > +**PHC timestamp**
> > +
> > +To retrieve PHC timestamp, use `ptp-userspace-api`_, usage example
> using `testptp`_:
> > +
> > +.. code-block:: shell
> > +
> > +  testptp -d /dev/ptp$(ethtool -T <interface> | awk '/PTP Hardware
> > + Clock:/ {print $NF}') -k 1
> 
> Why is not opening /dev/ptpX sufficient to enable the PHC?
> 
>     Andrew

Hi Andrew,

The reasoning for the enablement option of PHC was explained in patch 3 in the series
https://lore.kernel.org/netdev/20250304190504.3743-4-darinzon@amazon.com/

David