Re: [chrony-dev] SW/HW timestamping on Linux

[Denny Page <dennypage@xxxxxx>]

On Jan 18, 2017, at 05:43, Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:

Denny,

there is apparently a new ioctl for measuring the offset between the
NIC clock and system clock, which is supported on some onboard NICs
(that share clock with the CPU?). It's called PTP_SYS_OFFSET_PRECISE
and if I understand how it works correctly, it should solve all these
problems with delay and asymmetry. Is it supported on the i211 or
i350?

Miroslav,

Unfortunately, no. PTP_SYS_OFFSET_PRECISE uses PCIE_PTM (Precise Time Measurement) which requires newer PCIe chipsets. I don’t have a system that supports PTM. Best that I can tell, the only Ethernet driver in the kernel that currently offers PTM support is the Intel PCI-Express pro/1000 (E1000E), and I don’t have one of those either. Otherwise I would have added support for it in ethtscal. :)

https://pcisig.com/sites/default/files/specification_documents/ECN_PTM_Revision1a_31_Mar_2013.pdf

Denny