# Re: \[PATCH 2.6.21-rt2\] PowerPC: decrementer clockevent driver

- From: Segher Boessenkool \<hidden\>
- Date: 2007-05-17 19:27:28 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2007/05/957153
- Thread: https://ratatoskr.run/lkml/2007/05/957088/t.md

```text
> +	 * We must write a positive value to the decrementer to clear
> +	 * the interrupt on the IBM 970 CPU series.  In periodic mode,
> +	 * this happens when the decrementer gets reloaded later, but
> +	 * in one-shot mode, we have to do it here since an event handler
> +	 * may skip loading the new value...

Nothing special about 970 here -- on *every* PowerPC,
a decrementer exception exists as long as the high
bit of the decrementer equals 1.  BookE is different
of course.  Some other CPUs might deviate from the
architecture as well.


Segher
```