Messages in this thread | | | Date | Fri, 15 Feb 2013 14:34:33 -0800 | Subject | Re: timekeeping_adjust may set mult to 0 | From | John Stultz <> |
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On Mon, Feb 11, 2013 at 7:48 AM, David Engraf <david.engraf@sysgo.com> wrote: > I have encountered a problem when a linux system uses a clocksource with > mult = 1 and shift = 0 (clocksource cycle = nanoseconds). It may happen that > the function timekeeping_adjust reduces the value of mult to 0 when error is > lower than the interval [1]. > As soon as timekeeper.mult is 0, ktime_get will no longer work because it > uses timekeeping_get_ns which converts the cycle to nanoseconds with mult as > 0 and the system clocksource returns always 0.
So you *don't* want to use shift=0, since that kills the ability for the frequency adjustment code to do anything, as you've found.
Instead of calculating the clocksource mult/shift pair yourself, please use clocksource_register_hz/khz().
I'm hoping to kill off the open clocksource_register() call soon, to avoid this sort of confusion. Sorry for the trouble.
thanks -john
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