Re: [Linuxptp-users] offset explosion and irregular phc offsets

[Richard C. <ric...@gm...>]

On Mon, Aug 12, 2013 at 01:47:48PM +0100, Julien Houles wrote:
> 
> I've just tried with a normal linux kernel 3.9.11 and linuxptp 1.3.
> As with the other versions, I had to modify the phc2sys :
> No "if" for function "clock_gettime" error checking.
> 
> 
> because of the following error message :
> phc2sys -s p13p1 -O 0 -m
> phc2sys[707.070]: failed to read clock: Invalid argument

Can you be more specific? What have you changed?
Please show the diff.

  grep -nH -e "failed to read clock" *
  phc2sys.c:109:		pr_err("failed to read clock: %m");
  phc2sys.c:514:		pr_err("failed to read clock: %m");

Both of these cases should always work. If they don't, then your
system is broken.

> > This is only the apparent offset within the ptp4l program. The actual
> > offset is unknown to the program, but you can measure it using a PPS,
> > for example (but your hardware doesn't have this).
> 
> Sure, but I thought that a low and stable value of this apparent
> offset and delay would give us an indication on the good behaviour
> of the mechanism.

Yes, a low and stable value is a good sign. But bear in mind that the
hidden errors will accumulate when you cascade the nodes.

Thanks,
Richard