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

Hello.

Matt Sealey wrote:

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I haven't looked at all the new clock/timer code, is there any   
utility in having support for more than one clock source?

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  Of course, you may register as many as you like.

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Sure, but is there any utility in registering more than the  decrementer 
on PPC?

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   Not yet. I'm not sure I know any other PPC CPU facility fitting for 
clockevents. In theory, FIT could be used -- but its period is measured in 
powers of 2, IIRC.

Wouldn't it be possible to use SoC timer functionality, too, and not limit
this to what is only present on the CPU die?

    If you have some SoC timers, you're welcome to add support for it. :-)

I guess the real question is, how high resolution does a high resolution
timer need to be,

    In the order of microseconds.

 > and how often do you want to be handling interrupts?

    That depends on a kind of functionality you need: HRT and/or dynamic tick...

The 52XX has 8 general purpose timers and 2 slice timers. Both will
generate an interrupt once the clock hits a preset value, the timing
of which is determined by prescalers and the IPB clock..

WBR, Sergei