Well, scheduling using kernel timers is only going to give me a
frequency of at most 'HZ'
Which brings us back incrementing HZ, or using some other method.
--- In Fotis Loukos <> wrote:
>
> JD wrote:
> > I was wanting to a similar(ish) thing but writing out the I/O pins
> > instead.
> >
> > My thought was to create a driver attached to the 2nd timer of the cpu
> > and run the writing of the I/O in kernel land each time the timer
> > interrupt occurs.
> >
> > Looking a little closer at kernel code and the meager marvell CPU docs
> > I could find, it appears that both timer 1 & 2 share the same
> > interrupt (timer 1 being used for the system clock)
> >
> > Anyone know otherwise?
> >
> > I could add a shared interrupt I guess, if I made changes to the timer
> > to allow interrupt sharing, but I dont know if thats such a good
idea :)
>
> I think this is a BAD (TM) idea! Why don't you use kernel timers? You
> schedule a task to run after as many jiffies as you want. And since you
> know the HZ value you can convert this to msecs. But remember that since
> linux (the vanilla version of the kernel) is not a realtime os you can
> never be sure that a task you scheduled after x jiffies will run exactly
> after x jiffies!
>
> Fotis
>
> >
> >
> > --- In "fulatoro" <musaba@> wrote:
> >> Well, you might have a point, however, I am reading IO pins and I
> >> would like to have better granularity than the 10ms System clock, I
> >> realize that I can probably improve things by writing a device driver
> >> and doing the work in the kernel, but the complexity is not
justified.
> >> My system is doing basic IO work and provides a web interface for
> >> setup and configuration and that is about it. It should not be too
> >> taxing.
> >>
> >> Maybe someone else can share their experience on this.
> >>
> >> Moussa
> >>
> >> --- In Fotis Loukos <fotisl@> wrote:
> >>> fulatoro wrote:
> >>>> Hello, I was attempting to change the HZ setting and recompile the
> >>>> kernel but, I was unable to find the option when doing a make
> > xconfig.
> >>>> I did attempt to modify the .config file manually to set the HZ to
> >>>> 1000, but it seems to default back to 100. Any suggestions on
> > how to
> >>>> do this right?
> >>>>
> >>>> Moussa
> >>>>
> >>>>
> >>> Hello,
> >>> you can change the HZ value at linux/include/asm-arm/param.h.
But are
> >>> you sure you want to do this? 1000 interrupts per second just
for the
> >>> timer may be too much. At least for the user applications...
> >>>
> >>> Fotis
> >>>
> >
> >
> >
> >
> >
>
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