Messages in this thread | | | Date | Fri, 28 Feb 2020 10:15:07 -0800 | From | Richard Cochran <> | Subject | Re: [RFC PATCH v2 0/2] AT8031 PHY timestamping support |
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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
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