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

From: Segher Boessenkool <[email-masked]>
Date: Sat, 19 May 2007 14:28:14 +0200

>> Unfortunately, FIT exists only on Book E CPUs and MPC74xx aren't Book 
>> E, IIUC.
>
> By the name "FIT" perhaps, but MPC74xx has essentially
> the same thing.

> Set MMCR0[TBEE], set MMCR0[PMXE], and choose a TBL bit via 
> MMCR0[TBSEL].

That's the performance monitor, which could very well be
in use already (for performance monitoring stuff, who
would have guessed).

> It's also possible to trigger on the CPU cycle counter, but this would
> cost one of the performance counters. MPC7400 has 4, later CPUs have 6
> or more, and I think xPC7x0 had only 2.

7xx has at least four as well.

Segher