[Xenomai] powerpc 440 userspace latency test does nothing
steven.seeger at nasa.gov
Sun Dec 6 04:46:40 CET 2015
Me again. The issue appears to be that there's a discrepancy between the value
returned by clock_gettime(CLOCK_MONOTONIC... and the cobalt kernel's internal
notion of time. Changing latency to start with a 100 nanosecond relative time
(which adds some constant latency to the expected result since both the
expected and actual are no longer based on the same point in time) allows it
to run successfully.
It seems if I telnet into the board and generate too much text on the screen
the board locks up. I don't know if the board has any thermal cutoff (it gets
very hot) or if something is wrong with the kernel. I manually patched in some
vendor code from a 3.6 kernel into the 3.18.20 kernel to use the xenomai patch
so I could be missing something, too.
I'm not sure if this makes a difference, but here is clock_gettime's returned
tv_sec and tv_nsec (with a space in the middle) and the line after that is an
immediate read of ticks: from /proc/xenomai/clock/coreclk:
You can see there's an extra digit in the coreclk output compared to what
comes out of clock_gettime.
I went ahead and used the ipipe-core-3.14.39-powerpc-8 patch and built the
vendor's 3.14.2 kernel against it. I didn't have to do as much work as I did
with the 3.18.20 patch. I had the same results (both with latency and with
At this point I've got the answers I need from this exercise, but it would be
good to understand the problem and possibly fix it. If anyone can point me in
the right direction maybe I can take a look at it.
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