Hi Wolfgang, thanks! 10ns is excellent! I saw many references to DP83640 for PTP but we need to support Gb ethernet, I've found some Vitesse PHYs (VSC8572, VSC8574, VSC8582, VSC8584) that should also work for 1Gb ethernet, but I'm trying to find other alternatives, mainly because these PHYs have a limited temperature range (but similar to DP83640, 0 to 100C or -40 to 85C) and are a bit expensive. If you know any similar solutions for Gb ethernet please let me know.
Best regards Fernando On Wed, Sep 27, 2023 at 2:52 PM Wolfgang Hennig <when...@xia.com> wrote: > Just as a data point, I used the DP83640 PHY in the past and got about > 10ns, measured as the uncertainty in time-of-flight style physics > experiments. The PHY only supports 10/100M Ethernet, but is working with > LinuxPTP and can output synchronized clocks and triggers. > > Best regards, > > Wolfgang > > > On 9/27/2023 3:34 AM, Fernando Gomes wrote: > > Hi Richard, > > Thank you very much for your reply! We currently have a PTP implementation > done on an FPGA but we are looking for an alternative without using an FPGA > on simpler products. With the current implementation, we usually have an > accuracy better than 100ns (most of the time at around 60ns), this is why I > was considering the PHY tagging, to try to have the best possible accuracy > when using a CPU to implement PTP, but I don't know what accuracy is > possible when the timestamping is done at the MAC level and at the PHY > level, do you know if there is any benchmark about that? I saw some numbers > on a discussion saying that they had an accuracy of about 200ns with MAC > level timestamping, but having more consistent data will be great, 200ns > might not be acceptable for our application, we are going to do a > proof-of-concept to validate the results, but if we know beforehand the > achievable accuracy it could avoid to do extra effort if the required > accuracy is not achievable. > > Regarding the CPU we are currently evaluating, the ethtool -T results are > different on the two ethernet ports, which should be according to their > spec since they say they only support TSN in eth0: > > ethtool -T eth0 > Time stamping parameters for eth0: > Capabilities: > hardware-transmit > software-transmit > hardware-receive > software-receive > software-system-clock > hardware-raw-clock > PTP Hardware Clock: 1 > Hardware Transmit Timestamp Modes: > off > on > Hardware Receive Filter Modes: > none > all > ptpv1-l4-event > ptpv1-l4-sync > ptpv1-l4-delay-req > ptpv2-l4-event > ptpv2-l4-sync > ptpv2-l4-delay-req > ptpv2-event > ptpv2-sync > ptpv2-delay-req > > > ethtool -T eth1 > Time stamping parameters for eth1: > Capabilities: > hardware-transmit > software-transmit > hardware-receive > software-receive > software-system-clock > hardware-raw-clock > PTP Hardware Clock: 0 > Hardware Transmit Timestamp Modes: > off > on > Hardware Receive Filter Modes: > none > all > > From the ethtool -T results, the eth1 MAC doesn't have PTP-specific > Hardware Receive Filter Modes, but it still is capable of doing hardware > timestamping at the MAC level, right? > > Is it possible to use linuxptp to implement a one-step transparent clock? > For example, when using both eth0 and eth1 ports to implement HSR we need > the PTP messages passing by the device to be correctly adjusted to have a > precise time synchronization of all devices in the network (HSR ring). > > Best regards > > Fernando > > > > On Wed, Sep 27, 2023 at 3:47 AM Richard Cochran <richardcoch...@gmail.com> > wrote: > >> On Mon, Sep 25, 2023 at 02:36:35PM +0100, Fernando Gomes wrote: >> >> > Is there a list of hardware that can be used with linuxptp to do >> > timestamping at the hardware level (on PHY or on MAC)? There are some >> phys >> > that support it, like the Vitesse / Microchip, etc., but is there a >> > compatibility list available? >> >> I used to maintain a list of hardware, but I gave that up years ago >> when the number of products became too large. Nowadays most new MACs >> have PTP support. >> >> The easiest way to find out your MAC's capabilities is: >> >> ethtool -T eth0 >> >> For PHYs, the main issue is that the Linux networking stack doesn't >> treat MACs and PHYs equally. If you really need to use a PTP PHY, >> then you will likely have to configure and even patch your kernel >> specifically for your hardware. >> >> HTH, >> Richard >> > > > _______________________________________________ > Linuxptp-users mailing > listLinuxptp-users@lists.sourceforge.nethttps://lists.sourceforge.net/lists/listinfo/linuxptp-users > > > -- > Wolfgang Hennig, Ph.D. > XIA LLC > 2744 East 11th St, > Oakland, CA 94601 > >
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