> On Jan 18, 2017, at 09:11, Denny Page <dennyp...@me.com> wrote: > > >> On Jan 18, 2017, at 05:43, Miroslav Lichvar <mlich...@redhat.com >> <mailto:mlich...@redhat.com>> 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 > > <https://pcisig.com/sites/default/files/specification_documents/ECN_PTM_Revision1a_31_Mar_2013.pdf> > > 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
