Re: [PATCH] clockevents: Sanitize ticks to nsec conversion

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 09/17/2013 11:15 PM, Thomas Gleixner wrote:
> Marc Kleine-Budde pointed out, that commit 77cc982 "clocksource: use
> clockevents_config_and_register() where possible" caused a regression
> for some of the converted subarchs.
> 
> The reason is, that the clockevents core code converts the minimal
> hardware tick delta to a nanosecond value for core internal
> usage. This conversion is affected by integer math rounding loss, so
> the backwards conversion to hardware ticks will likely result in a
> value which is less than the configured hardware limitation. The
> affected subarchs used their own workaround (SIGH!) which got lost in
> the conversion.
> 
> Now instead of fixing the underlying core code problem, Marcs patch
> tried to work around the core code issue by increasing the minimal
> tick delta at clockevents registration time so the resulting limit in
> the core code backwards conversion did not violate the hardware
> limits. More SIGH!

It was not easy getting your attention with this problem :)

Marc

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Pengutronix e.K.                  | Marc Kleine-Budde           |
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