Messages in this thread | | | From | Segher Boessenkool <> | Subject | Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver | Date | Thu, 17 May 2007 21:50:52 +0200 |
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>>> + * 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. > > Quoting "PowerPC Operating Environment Architecture":
<snip>
> Otherwise, when the contents of DEC0 change, the exception effects of > the Decrementer become consistent with the new contents of the > Decrementer reasonably soon after the change.
And that is guaranteed on all PowerPC as far as I can see. The main thing is that a decrementer exception won't go away until the high bit becomes 0.
Segher
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