NAME

       phc_ctl - directly control PHC device clock

SYNOPSIS

       phc_ctl [ options ] <device> [ commands ]

DESCRIPTION

       phc_ctl is a program which can be used to directly control a PHC clock device.  Typically,
       it is used for debugging purposes, and has little use for general control of  the  device.
       For general control of PHC clock devices, phc2sys (8) should be preferred.

       <device>  may be either CLOCK_REALTIME, any /dev/ptpX device, or any ethernet device which
       supports ethtool's get_ts_info ioctl.

OPTIONS

       -l print-level
              Set the maximum syslog level of messages which should be printed  or  sent  to  the
              system logger. The default is 6 (LOG_INFO).

       -q     Do not send messages to syslog. By default messages will be sent.

       -Q     Do not print messages to standard output. By default messages will be printed.

       -h     Display a help message.

       -v     Prints the software version and exits.

COMMANDS

       phc_ctl  is  controlled  by  passing  commands  which  take either an optional or required
       parameter. The commands (outlined below) will control aspects of  the  PHC  clock  device.
       These  commands  may  be  useful  for inspecting or debugging the PHC driver, but may have
       adverse side effects on running instances of ptp4l (8) or phc2sys (8)

       set seconds
              Set the PHC clock time to the value  specified  in  seconds.  Defaults  to  reading
              CLOCK_REALTIME if no value is provided.

       get    Get the current time of the PHC clock device.

       adj seconds
              Adjust the PHC clock by an amount of seconds provided. This argument is required.

       freq ppb
              Adjust  the  frequency  of  the PHC clock by the specified parts per billion. If no
              argument is provided, it will attempt to read the current frequency and report it.

       cmp    Compare the PHC clock device to CLOCK_REALTIME, using the best method available.

       caps   Display the device capabilities. This is the default command  if  no  commands  are
              provided.

       wait seconds
              Sleep  the  process  for  the  specified  period  of  time,  waking up and resuming
              afterwards. This command may be useful for sanity checking whether the PHC clock is
              running as expected.

              The  arguments  specified  in  seconds  are read as double precision floating point
              values, and will scale to nanoseconds. This means providing a value of 5.5 means  5
              and one half seconds. This allows specifying fairly precise values for time.

EXAMPLES

       Read the current clock time from the device
              phc_ctl /dev/ptp0 get

       Set the PHC clock time to CLOCK_REALTIME
              phc_ctl /dev/ptp0 set

       Set PHC clock time to 0 (seconds since Epoch)
              phc_ctl /dev/ptp0 set 0.0

       Quickly  sanity  check  frequency  slewing  by  setting slewing frequency by positive 10%,
       resetting clock to 0.0 time, waiting for 10 seconds, and then reading time. The time  read
       back should be (roughly) 11 seconds, since the clock was slewed 10% faster.
              phc_ctl /dev/ptp0 freq 100000000 set 0.0 wait 10.0 get

SEE ALSO

       ptp4l(8) phc2sys(8)