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. :)
Denny
And To be clear, this would not address phy/mac delay/asymmetry issues. It would just replace the call to PTP_SYS_OFFSET. Instead of an array that you have to interpolate, you just get a single (accurate) value. This would be very helpful however, because PTP_SYS_OFFSET is the source of most of the variance in ethtscal.
Denny
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