Advanced PTP Configuration¶

Caution

Parameters are written to the ptp4l configuration file without error checking. Caution must be taken to ensure that parameter names and values are correct as errors will cause ptp4l launch failures.

Configure ITU-T G.8275.1 Grandmaster Settings Fields¶

Users can configure ptp4l instances to set the PTP Announce messages fields in conformance with the ITU-T G.8275.1/Y.1369.1 PTP profile. This configuration is recommended for nodes that are configured as a T-GM or T-BC and using the G.8275.1 PTP profile.

Prerequisites

The system should be configured with at least one ptp4l instance. See Configure PTP Service Using the CLI for more information.
Any ptp4l instances using the G.8275.1 profile must be configured with the dataset_comparison=G.8275.x instance parameter. This parameter enables the G.8275.1 PTP profile for the ptp4l instance.
```
~(keystone_admin)]$ system ptp-instance-parameter-add <ptp4l instance> dataset_comparison=G.8275.x
```

About this task

The following section provides additional details about the relevant Announce message fields and how to configure their value.

507c6f.fffe.21bb24-0 seq 0 RESPONSE MANAGEMENT GRANDMASTER_SETTINGS_NP
        clockClass              6
        clockAccuracy           0x20
        offsetScaledLogVariance 0x4e5d
        currentUtcOffset        37
        leap61                  0
        leap59                  0
        currentUtcOffsetValid   1
        ptpTimescale            1
        timeTraceable           1
        frequencyTraceable      1
        timeSource              0x20

Each of the fields are explained below:

clockClass

This field is dynamically set by StarlingX based on the state of the Primary Reference Time Clock (PRTC) used by the ptp4l instance. No user configuration is required.

clockAccuracy

Default value (not locked to PRTC): 0xfe

Default value (locked to PRTC): 0x20

When a ptp4l instance is locked to a PRTC, the value will be dynamically updated to 0x20.

If the ptp4l instance is connected to an Enhanced Primary Reference Time Clock (ePRTC), the locked value can be changed by using a ptp4l instance parameter.

~(keystone_admin)]$ system ptp-instance-parameter-add <ptp4l instance> clockAccuracy=0x21

offsetScaledLogVariance

Default value (not locked to PRTC): 0xffff

Default value (locked to PRTC): 0x4e5d

The offsetScaledLogVariance attribute characterizes the stability of the clock. If the ptp4l instance is connected to an ePRTC, the locked value can be changed by using a ptp4l instance parameter.

~(keystone_admin)]$ system ptp-instance-parameter-add <ptp4l instance> offsetScaledLogVariance=0x4b32

currentUtcOffset

Default value: 37

The current offset between TAI and UTC. This value does not need to be altered unless IERS introduces a new leapsecond into UTC. If necessary, the value can be altered for testing purposes using a ptp4l instance parameter.

~(keystone_admin)]$ system ptp-instance-parameter-add <ptp4l instance> utc_offset=37

leap61

Default value: 0

This attribute is used to handle the addition of a new leapsecond. StarlingX does not currently support altering the leap61 attribute.

leap59

Default value: 0

This attribute is used to handle the addition of a new leapsecond. StarlingX does not currently support altering the leap59 attribute.

currentUtcOffsetValid

Default value: 0

This value should be set to 1 in order to indicate that currentUtcOffset value is correct and suitable for use by downstream nodes. The attribute can be altered using a ptp4l instance parameter.

~(keystone_admin)]$ system ptp-instance-parameter-add <ptp4l instance> currentUtcOffsetValid=1

ptpTimescale

Default value: 1

This attribute should always be set to 1 according to the G.8275.1 PTP profile.

timeTraceable

Default value: 0

This attribute is dynamically set by StarlingX based on the ptp4l instance’s connection to a PRTC. When a PRTC is connected to the ptp4l instance, timeTraceable will be set to 1.

frequencyTraceable

Default value: 0

This attribute is dynamically set by StarlingX based on the ptp4l instance’s connection to a PRTC. When a PRTC with frequency information is connected to the ptp4l instance, frequencyTraceable will be set to 1.

timeSource

Default value: 0xa0

This attribute describes the type of clock used for the PRTC. The default value of 0xa0 indicates the use of an internal oscillator on the PTP NIC. StarlingX will automatically update this value to 0x20 (GPS) if it detects that the ptp4l instance is utilizing a GPS time source.

Users can change this attribute using a ptp4l instance parameter. For a comprehensive list of time source types and their respective values, consult the G.8275.1 standard.

~(keystone_admin)]$ system ptp-instance-parameter-add <ptp4l instance> timeSource=0x20

Apply PTP configuration¶

After assigning ptp4l instance parameters, apply the new PTP configuration using system ptp-instance-apply.

Verify Announce Message Attributes¶

The PTP Announce Message Attributes can be viewed using the pmc tool.

sudo pmc -u -b 0 -f /etc/linuxptp/ptpinstance/<ptp4l instance config file> 'GET GRANDMASTER_SETTINGS_NP'

sending: GET GRANDMASTER_SETTINGS_NP
  507c6f.fffe.21bb24-0 seq 0 RESPONSE MANAGEMENT GRANDMASTER_SETTINGS_NP
          clockClass              6
          clockAccuracy           0x20
          offsetScaledLogVariance 0x4e5d
          currentUtcOffset        37
          leap61                  0
          leap59                  0
          currentUtcOffsetValid   1
          ptpTimescale            1
          timeTraceable           1
          frequencyTraceable      1
          timeSource              0x20

The log output for dynamically updated values can be found in /var/log/collectd.log.