[okl4-developer] [Developer] counting timer tick interrupts, what for?

[Carl van Schaik]

Hi Jorge,

Yeah, you can change the timer tick oeriof fairly easily.

in the platform code, there should be a define eg:
#define TIMER_TICK_LENGTH      5000

which says period of 5000us = 200Hz

change this value, and make sure the platform timer code sets up the 
correct frequency. Unfortunately, many of the old platform timer drivers 
have a hardcoded timer period so you can't just change the 
TIMER_TICK_LENGTH value and hope everything works.

regards,
Carl

Jorge Torres wrote:
> Thanks Carl,
>
> About what I meant by "tick-width", well, I guess it is time tick 
> period. sorry about that; some times I can't remember the right 
> English word! :)
>
> Cheers,
>
>
> On 5/13/07, *Carl van Schaik* <carl at ok-labs.com 
> <mailto:carl at ok-labs.com>> wrote:
>
>     Hi Jorge,
>
>     Jorge Torres wrote:
>     > Hi everyone,
>     >
>     > Please correct me if I'm wrong:
>     >
>     > IRQ Time tick interrupts are passed to
>     the  timer_interrupt  function
>     > (for  ia32:  pistachio/arch/ia32/src/timer.cc),  who attends it,
>     and
>     > passes it to the scheduler's handle_timer_interrupt method, right?
>     Correct
>
>     > Two things I don't understand: what for is the timetick handler
>     > keeping a counter (ticks++)?
>     > is the time tick something I can specify/modify at run time?,
>     how can
>     > I change such ticktime  width?
>     The ticks count used to be used in really old versions of the
>     kernel for
>     timeout calculations. This is no longer the case. The only thing
>     currently using the ticks count is the tracebuffer code which uses it
>     for timestamps. The ticks value is not generally available to
>     user-land
>     code so in that sense, it could be removed when the tracebuffer is not
>     required.
>     Not sure what you are asking about tick-width.
>     > Oh yes, another thing, I have some free time, and I would like
>     to help
>     > on this elegant irq interrupts handler registration proposed  on
>     OKL4
>     > (irq_manager.register(hwirq, #, FUNCTION)), what is it there to do?
>     I'm not an ia32 person, but I guess what they where after was a class
>     that handled the irq related stuff (ie irq_manager). A method of the
>     class would then be used to do the appropriate IDT etc manipulation
>     stuff. I guess that they would want the irq manager to handle multiple
>     levels of interrupt controllers and different hardware types.
>     >
>     > Thank you very much,
>     >
>     > Jorge
>     regards,
>     Carl
>
>