Re: [Linuxptp-users] Synchronization fault with stmmac

[Mohamed B. <mbe...@ad...>]

> On Wed, 2014-03-19 at 10:46 +0100, Richard Cochran wrote:
> > On Wed, Mar 19, 2014 at 09:54:00AM +0100, Mohamed Belaouad wrote:
> > 
> > > From the first test I did (running ptp4l to get the PC time then
> > > stopping it), the board ptp time seems to run slower than the PC
> > > time. While 5 minutes elapsed on the PC, 2/3min only do on the
> > > board.
> > 
> > You can easily test the clock speed like this.
> > 
> >     testptp -g
> >     sleep 60
> >     testptp -g
> > 
> > Then, see if 60 seconds elapsed.
> > 

This is now working correctly after setting the correct frequencies in the driver. There is no more synchronization fault :).

> 
> Also test with various adjustment frequencies applied, I don't know
> exact commands here, but you can do something like:
> 
> adjust frequency by 50% (500 million ppb)
> set clock to system time or 0
> get time
> sleep some amount of time
> get time
> 
> then check to see if the expected time adjusted by the frequency change
> has actually passed.
> 
> In this way, you can see whether frequency adjustment is working right,
> since if you modify the clock frequency by say.. 1.5x, then you should
> see roughly an equivalent decrease in the time different on clock, of
> "time difference / 1.5".
> 
> Please do these experiments using testptp first and see if things make
> sense. This will help limit the scope of the tests so you can see what
> parts might be failing.
> 
> I would suggest attempting to set the ppb to the maximum value your
> driver allows as well, to check to see if the adjustment is overflowing
> somehow.

The driver implementation is not checking the max frequency adjustment...
I still did some tests and strange enough there is a value change to -32,768,000 when passing ppb greater than 32,768,000. Also, the value saturates to -32,768,000 with ppb lesser than -32,768,000.
So I am forced to use values between [-32,768,000 | 32,768,000]. I guess your test suggestion will pass once I get through this.

Could you please shed some light on that? Is it something related with the kernel ptp clock driver? I did not find 

The value received by the driver is the one after ppb:
TEST PTP ADJ FREQ:
# ./testptp -d /dev/ptp0 -f 32767999
[ADJ_FREQ 0] ppb:32767999
frequency adjustment okay
# ./testptp -d /dev/ptp0 -f 32768000
[ADJ_FREQ 0] ppb:-32768000
frequency adjustment okay
# ./testptp -d /dev/ptp0 -f -32768000
[ADJ_FREQ 0] ppb:-32768000
frequency adjustment okay
# ./testptp -d /dev/ptp0 -f -32768001
[ADJ_FREQ 0] ppb:-32768000
frequency adjustment okay

Thanks,
Mohamed