Re: [Linuxptp-users] Interesting (very wrong) PTP output

[Jacob K. <jac...@in...>]

On 09/25/2012 01:10 AM, Richard Cochran wrote:
> On Thu, Jun 07, 2012 at 11:54:48AM +0200, Christian Riesch wrote:
>>
>> Please find below a patch (it's only an quick hack and only compile-tested)
>> that
>> a) sets the clock to 0 ppb before doing anything else,
>> b) clamps s->drift to the maximum adjustment value at the first calculation
>>     (estimation),
>> c) applies the estimate to the clock.
>
> Coming back to this patch, I think I now have a better solution to the
> issue of starting with a clock that has already been adjusted. I just
> pushed out this commit
>
>     8f00d29 Discover and utilize the initial clock frequency adjustment.
>
> that makes use of the clock_adjtimex() to get the initial frequency
> adjustment value (functionality to appear in kernel 3.7).
>
> FWIW, I did try out this patch, but I found that, suprisingly, the
> code seemed to work better without this patch.  I think the reason
> was that the path delay measurements were spoiled by resetting the
> frequency adjustment to zero, and the circa 100 ppm error introduced
> at the jump was soon corrected.
>
> In any case, using the latest kernel together with this patch works
> perfectly, tested using the PHYTER.
>
> Thanks,
> Richard
>
>

Once I have a spare moment I will go ahead and test this on the intel 
ixgbe parts. It should provide a definite improvement.

- Jake