PTP

I recently started looking into how PTP works and what the possibilites for hardware assisted time stamping is.

Here are some random notes:

• Using chrony for combining ptp and ntp
• PTP hardware clock in chrony (see the PHC section)
• Super fancy Intel NIC with two PPS in/out connectors It also has a higher quality crystal than usual. Seems to retail for somewhere around $1000.
• PTP performance with software timestamping by Emil Gedda and Anders Eriksson
• configuring ptp4l
• Using ptp4l/phc2sys
• Meinberg blog on PTP
• Using a apu2c0 board with hardware timestamping by Dan Drown. Seems like thic cheap board has an Intel NIC with hardware support for PPS time stamping.
• Teklager sells the APU2E0 for approx SEK 2000
• The interesting part on the Intel NIC is the “software defined pins”. See this support question which links to a datasheet. There is a description how to read the time for external interrupts.
• There is a relatively cheap Intel i210 nic with a connector. I have not yet found a description of what signals the connector has.
• using the sdp output
• Hardware assisted COTS IEEE 1588 solution for x86 Linux and its performance evaluation, by Balint Ferencz and Tamás Kovácsházy.

I am interested in what performance one can get from a using the ptp4l and a reasonably priced NIC.

I discovered that a Gigabyte Brix, which I use as a power efficient server, has an Intel NIC with hardware support (but does not seem to support PPS in):

root@server:~# ethtool -T enp0s31f6
Time stamping parameters for enp0s31f6:
Capabilities:
    hardware-transmit     (SOF_TIMESTAMPING_TX_HARDWARE)
    software-transmit     (SOF_TIMESTAMPING_TX_SOFTWARE)
    hardware-receive      (SOF_TIMESTAMPING_RX_HARDWARE)
    software-receive      (SOF_TIMESTAMPING_RX_SOFTWARE)
    software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
    hardware-raw-clock    (SOF_TIMESTAMPING_RAW_HARDWARE)
PTP Hardware Clock: 0
Hardware Transmit Timestamp Modes:
    off                   (HWTSTAMP_TX_OFF)
    on                    (HWTSTAMP_TX_ON)
Hardware Receive Filter Modes:
    none                  (HWTSTAMP_FILTER_NONE)
    all                   (HWTSTAMP_FILTER_ALL)
    ptpv1-l4-sync         (HWTSTAMP_FILTER_PTP_V1_L4_SYNC)
    ptpv1-l4-delay-req    (HWTSTAMP_FILTER_PTP_V1_L4_DELAY_REQ)
    ptpv2-l4-sync         (HWTSTAMP_FILTER_PTP_V2_L4_SYNC)
    ptpv2-l4-delay-req    (HWTSTAMP_FILTER_PTP_V2_L4_DELAY_REQ)
    ptpv2-l2-sync         (HWTSTAMP_FILTER_PTP_V2_L2_SYNC)
    ptpv2-l2-delay-req    (HWTSTAMP_FILTER_PTP_V2_L2_DELAY_REQ)
    ptpv2-event           (HWTSTAMP_FILTER_PTP_V2_EVENT)
    ptpv2-sync            (HWTSTAMP_FILTER_PTP_V2_SYNC)
    ptpv2-delay-req       (HWTSTAMP_FILTER_PTP_V2_DELAY_REQ)

The NIC seems to be a I219, lspci gives 00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection I219-V (rev 21). The product pages lists is as IEEE1588 enabled.