On Fri, Jan 15, 2021 at 11:32:47AM +0000, Coughlin, David S wrote:
> I'm using an Extreme Engineering XPort 3200 grandmaster clock in my
> system. It expects to get its base timing signal from a 1PPS signal
> driven by an ICD-GPS-153 compliant receiver, and publish it via ptp.
> I had to work out an upstream replacement for the stock ts2phc, and
> as I fix my last bugs on that I have a question about its behavior.
> When the board comes up cold, the clock just runs from zero in both
> the phc clock and system clock on the board. The current UTC time
> is a long way from zero. Will ts2phc try to steer it to current
> time, or will it recognize that there is a big gap, and just reset
> the phc clock? Likewise, will phc2sys steer the system clock or
> jump it?
All of the programs that have a servo, ptp4l, phc2sys, and ts2phc,
accept configuration options that control the stepping behavior.
step_threshold
The maximum offset the servo will correct by changing the clock
frequency instead of stepping the clock. When set to 0.0, the
servo will never step the clock except on start. It's specified
in seconds. The default is 0.0. This option used to be called
pi_offset_const.
first_step_threshold
The maximum offset the servo will correct by changing the clock
frequency instead of stepping the clock. This is only applied on
the first update. It's specified in seconds. When set to 0.0,
the servo won't step the clock on start. The default is 0.00002
(20 microseconds). This option used to be called pi_f_off-
set_const.
HTH,
Richard
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