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

[Jakub Kicinski <kuba@kernel.org>]

On Sat, 25 Jul 2026 17:54:53 +0200 Andrew Lunn wrote:
> 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.

Ack, thanks! To clarify I of course don't mind modification one-step
timestamping style (Tx). But here we're overriding reserved protocol
fields to carry local metadata (Rx).

Let's see v4..