Re: [PATCH] dynamic tick patch

[George Anzinger <george@mvista.com>]

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@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/