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<== Date ==> <== Thread ==>
Subject: Power PMAC and EPICS Time stamps
From: Choon Lim <[email protected]>
To: [email protected]
Date: Tue, 29 Jul 2014 15:24:44 -0700
Hello, 

We use Power PMAC(s) for Insertion Device motion controls.  soft IOCs run on the Power PMACs. 

As most of you already know, the Power PMAC runs Linux with a Xenomai real time kernel. 

We have been trying to determine why the EPICS time stamps have been incorrect.

We determined that after a reboot of the machine:
- clock_gettime(CLOCK_REALTIME, &clockNow) functions would return the time since reboot.  This does not correlate with the Xenomai API which states it should be the time since EPOCH 

- As a result when the first IOC is launched after a reboot, the following logic from /src/libCom/osi/osiClockTime.c is invoked 
    if (!ClockTimePvt.synchronized &&
        clockNow.tv_sec < POSIX_TIME_AT_EPICS_EPOCH) {
        clockNow.tv_sec = POSIX_TIME_AT_EPICS_EPOCH + 86400;
        clockNow.tv_nsec = 0;
        clock_settime(CLOCK_REALTIME, &clockNow);
        errlogPrintf("WARNING: OS Clock time was read before being set.\n"
            "Using 1990-01-02 00:00:00.000000 UTC\n");
    }

- This then sets the time to 1990-01-02 after which subsequent IOCs use this time 

- Strangely the time() function in <time.h> returns the correct time regardless of whether the machine has been rebooted. 

- I have contacted Delta Tau and asked them if they know about this phenomenon

- As a "quick" fix to the issue, I am calling clock_settime() with the value of time() after a reboot, however I do not think this allows for NTP corrections.  

I hope this helps anyone else out there who is enjoying the "nuances" or the Power PMAC. 

Choon  
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