Re: [chrony-users] hwtimestamp

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On Fri, Jul 31, 2020 at 9:48 AM Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:
> No, that doesn't look right. There should be an "H" in the log, at
> least for some entries. What NIC driver does it use? Does it work with
> ptp4l? Maybe the HW can get a transmit HW timestamp only for PTP
> packets. A Broadcom 10gb NIC has this weird limitation, which cannot
> be described in the Linux timestamping API.

Hi Miroslav, thanks.

It's a Texas Instruments CPSW (Beaglebone), and looking at the code it
is unsupported on the receiving side:

https://github.com/torvalds/linux/blob/e8407fdeb9a6866784e249881f6c786a0835faba/drivers/net/ethernet/ti/cpsw_priv.c#L641

This is what ethtool and Chrony correctly identifies ("Enabled HW
timestamping (TX only)").

I so assume as you say that since this is not working, and the
hardware does not support non PTP RX timestamps, it is very likely
that it would not support this on the TX side.

I couldn't find any information about it to confirm though.

Thanks,
Nuno

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