Re: [Linuxptp-users] Hardware PTP clock synchronization

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

On Mon, Aug 05, 2013 at 09:56:23AM +0300, Гаврилов Александр wrote:
> Hello!
> 
> Here is an example of the log where synchronization occured:

This is interesting...

> ptp4l -2 -i p16p1 -m -H -s
> ptp4l[17534.938]: selected /dev/ptp0 as PTP clock
> ptp4l[17534.957]: port 1: INITIALIZING to LISTENING on INITIALIZE
> ptp4l[17534.957]: port 0: INITIALIZING to LISTENING on INITIALIZE
> ptp4l[17536.761]: port 1: new foreign master ece555.fffe.2de639-2
> ptp4l[17540.751]: selected best master clock ece555.fffe.2de639
> ptp4l[17540.751]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
> ptp4l[17542.696]: port 1: minimum delay request interval 2^3

The average delay request interval is eight seconds.

> ptp4l[17542.746]: master offset 50001478246023551 s0 adj      +0 path delay       1276
> ptp4l[17543.744]: master offset 50001478246021573 s0 adj      +0 path delay        974
> ptp4l[17544.741]: master offset 50001478246019277 s0 adj      +0 path delay        974
> ptp4l[17545.739]: master offset 50001478246016997 s1 adj      +0 path delay        974
> ptp4l[17546.736]: master offset      -5048 s2 adj   -5048 path delay        974
> ptp4l[17546.736]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
> ptp4l[17547.734]: master offset      -2323 s2 adj   -3837 path delay        974
> ptp4l[17548.732]: master offset       -789 s2 adj   -3000 path delay        974
> ptp4l[17549.729]: master offset        -95 s2 adj   -2543 path delay        974
> ptp4l[17550.726]: master offset        123 s2 adj   -2354 path delay        974
> ptp4l[17551.724]: master offset        110 s2 adj   -2330 path delay        974
> ptp4l[17552.721]: master offset        106 s2 adj   -2301 path delay        974
> ptp4l[17553.719]: master offset        109 s2 adj   -2266 path delay        974
> ptp4l[17554.716]: master offset        104 s2 adj   -2238 path delay        974
> ptp4l[17555.714]: master offset        -27 s2 adj   -2338 path delay        974
> ptp4l[17556.711]: master offset        -48 s2 adj   -2367 path delay        974
> ptp4l[17557.709]: master offset        -53 s2 adj   -2386 path delay        974
> ptp4l[17558.706]: master offset         45 s2 adj   -2304 path delay        974

Looking at the last column (moving average of the path delay), you
have two successful path delay measurements ...

> ptp4l[17559.704]: master offset        275 s2 adj   -2061 path delay        716

... now three ...

> ptp4l[17560.701]: master offset          9 s2 adj   -2244 path delay        716
> ptp4l[17561.699]: master offset       -131 s2 adj   -2382 path delay        716
> ptp4l[17562.696]: master offset       -176 s2 adj   -2466 path delay        716
> ptp4l[17563.694]: master offset       -102 s2 adj   -2445 path delay        716
> ptp4l[17564.691]: master offset        -28 s2 adj   -2401 path delay        716
> ptp4l[17565.689]: master offset         47 s2 adj   -2335 path delay        716
> ptp4l[17566.686]: master offset          2 s2 adj   -2366 path delay        716
> ptp4l[17567.684]: master offset        -27 s2 adj   -2394 path delay        716
> ptp4l[17568.681]: master offset         40 s2 adj   -2335 path delay        716
> ptp4l[17569.679]: master offset        -13 s2 adj   -2376 path delay        716
> ptp4l[17570.676]: master offset         69 s2 adj   -2298 path delay        589

... and now four ...

> ptp4l[17571.674]: master offset          9 s2 adj   -2337 path delay        589
> ptp4l[17572.671]: master offset        -52 s2 adj   -2396 path delay        589
> ptp4l[17572.955]: recvmsg tx timestamp failed: Resource temporarily unavailable
> ptp4l[17572.955]: port 1: send delay request failed

... and the fifth one fails.

> ptp4l[17572.955]: port 1: SLAVE to FAULTY on FAULT_DETECTED
> ptp4l[17591.068]: port 1: FAULTY to LISTENING on FAULT_CLEARED
> ptp4l[17592.622]: port 1: new foreign master ece555.fffe.2de639-2
> ptp4l[17596.612]: selected best master clock ece555.fffe.2de639
> ptp4l[17596.612]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
> ptp4l[17597.609]: master offset       1492 s2 adj    -867 path delay        589
> ptp4l[17597.609]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
> ptp4l[17597.654]: recvmsg tx timestamp failed: Resource temporarily unavailable
> ptp4l[17597.654]: port 1: send delay request failed
> ptp4l[17597.654]: port 1: SLAVE to FAULTY on FAULT_DETECTED

In order to get the best out of the 82576, I recommend:

1. Make sure you are using the latest version (ptp4l -v).

2. Set tx_timestamp_timeout to 1000.

3. Set fault_reset_interval to ASAP.

4. If the above steps do not yield reasonable results, then recompile
   the driver, changing IGB_PTP_TX_TIMEOUT from (HZ * 15) to (HZ).

It appears that the hardware is sometimes missing or dropping the Tx
time stamp on the delay request messages. Changing IGB_PTP_TX_TIMEOUT
will clear the driver's Tx time stamp timer more often. This might
make the card more responsive in the presence of time stamp loss.

Good luck,
Richard