Re: [PATCH net-next v3 0/3] net: dsa: mv88e6xxx: various hwstamp fixes

[Andrew Lunn]

On Fri, Jul 24, 2026 at 04:52:07PM -0700, Jakub Kicinski wrote:
> On Sun, 19 Jul 2026 15:30:52 +1000 Luke Howard wrote:
> > Three fixes for improving the reliably of hardware timestamp acquisition
> > on Marvell switches. In our tests this eliminated missed timestamps in
> > ptp4l, whilst also preserving PTP event and general message ordering on
> > switches that support embedded timestamps.
> 
> Do you know if there's any precedent in the existing upstream drivers
> for overriding the reserved bytes? It's not normal for devices to modify
> the ingress frames. Perhaps there's some precedent, but if not I think
> we should gate this (eg with a devlink param?)
> 
> Andrew, do you have any opinion? Or perhaps Richard?

I have a dim memory of PHYs who change the packet by adding time
stamps. There are definitely DSA switches which can put the stamps in
the DSA header/trailer.

    Andrew