Hi, For TSN, we need jitter of ~ 100 nanoseconds, And most interface can issue a jitter of ~10 nanoseconds. So for now TSN does not need fractions of nanosecond. Further more, I do not think there is any Ethernet based traffic that can benefit from such accuracy. As for 1 Gigabits, each bit is nanoseconds so the phy is not sensitive for less. It is only make sense to have PHC of fractional nanoseconds if you can set the PTP to accuracy < 2 nanoseconds, I mean master offset and time adjust of less then. May be when 10 Gigabits or higher throughput goes to end device, it will make sense.
Erez -----Original Message----- From: Richard Cochran <richardcoch...@gmail.com> Sent: Sunday, 24 May 2020 18:33 To: FUSTE Emmanuel <emmanuel.fu...@thalesgroup.com> Cc: linuxptp-devel@lists.sourceforge.net Subject: Re: [Linuxptp-devel] [PATCH V1 2/2] Add support for write phase mode. On Mon, May 18, 2020 at 07:58:47AM +0000, FUSTE Emmanuel wrote: > Perhaps too late, and should have been raised on netdev but why ns > granularity for phase adjustment ? This comes from the traditional NTP timex interface. > Talking about net device phc clock and phase adjustment I directly > think "white rabbit". If your PHC is locked on the ethernet carrier > (SyncE), the final step is phase adjustment to go to sub ns sync. > Choosing ps granularity would be more future proof for the interface > and would allow to expose white rabbit hardware clock/board as a PHC > and implement the WR control plane in userspace using standard > interface (would need more extension, but it is a start). I think it wouldn't be hard to extend the interface. You could take one of the unused 32 bit fields and make that fractional nanoseconds, for example. If white rabbit wants to submit an patch to the kernel along with a driver, then I would support the idea. Thanks, Richard _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.sourceforge.net%2Flists%2Flistinfo%2Flinuxptp-devel&data=02%7C01%7Cerez.geva.ext%40siemens.com%7Ceeb3d8bedb8f4424853d08d8000047ad%7C38ae3bcd95794fd4addab42e1495d55a%7C1%7C0%7C637259348485004077&sdata=5ORoy2eXzrwJI4ETgsbfUIbhLpb4ZlpKDvnm5jRk%2BXI%3D&reserved=0 _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
