Re: [PATCH] dynamic tick patch

[George Anzinger]

Zwane Mwaikambo wrote:
> On Fri, 21 Jan 2005, Tony Lindgren wrote:
>
>
> > > This doesn't seem to cover the local APIC timer, what do you do about the 
> > > 1kHz tick which it's programmed to do?
> >
> > Sorry for the delay in replaying. Thanks for pointing that out, I
> > don't know yet what to do with the local APIC timer. Have to look at
> > more.
>
>
> Pavel does your test system have a Local APIC? If so that may also explain 
> why you didn't see a difference.
>
> Tony, something like the following for oneshot should work, untested of 
> course. Perhaps you could use that for the wakeup interrupt instead?
>
> void setup_oneshot_apic_timer(unsigned int count)
> {
> 	unsigned int lvtt, tmp_value;
> 	unsigned long flags;
>
> 	count *= calibration_result;
> 	local_irq_save(flags);
> 	lvtt = ~APIC_LVT_TIMER_PERIODIC | LOCAL_TIMER_VECTOR;
> 	apic_write_around(APIC_LVTT, lvtt);
> 	tmp_value = apic_read(APIC_TDCR);
> 	apic_write_around(APIC_TDCR, (tmp_value
> 			& ~(APIC_TDR_DIV_1 | APIC_TDR_DIV_TMBASE))
> 			| APIC_TDR_DIV_16);
>
> 	apic_write_around(APIC_TMICT, count/APIC_DIVISOR);
> 	local_irq_restore(flags);
> }

The VST patch on sourceforge (http://sourceforge.net/projects/high-res-timers/) 
uses the local apic timer to do the wake up.  This is the same timer that is 
used for the High Res work.

--
George Anzinger   george@xxxxxxxxxx
High-res-timers:  http://sourceforge.net/projects/high-res-timers/

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