On Fri, Feb 28, 2020 at 07:02:24PM +0100, Michael Walle wrote:

 (1) The PHY doesn't support atomic reading of the (timestamp,
     messageType, sequenceId) tuple. The workaround is to read the
     timestamp again and check if it has changed. Actually, you'd have
     to read the complete tuple again.

This HW is broken by design :(

But if you're using a P2P clock with peer delay requests this whole
thing falls apart because of caveat (3). You'll often see messages like
  received SYNC without timestamp
or
 received PDELAY_RESP without timestamp
in linuxptp. Sometimes it working for some time and then it starts to
loosing packets. I suspect this depends on how the PDELAY messages are
interleaved with the SYNC message. If there is not enough time to until
the next event message is received either of these two messages won't
have a timestamp.

And even the case where a Sync and a DelayResp arrive at nearly the
same time will fail.

The PHY also supports appending the timestamp to the actual ethernet frame,
but this seems to only work when the PHY is connected via RGMII. I've never
get it to work with a SGMII connection.

This is the way to go.  I would try to get the vendor's help in making
this work.

Thanks,
Richard