Re: Two timer in FIQ mode

["Sicheri Marco" <m.sicheri@ctsgroup.it>]

You (Andrew and Mark) wrote:

> On Fri, 2004-11-19 at 07:35, Andrew Lunn wrote:
> > On Fri, Nov 19, 2004 at 11:43:39AM +0100, Sicheri Marco wrote:
> > > I all,
> > > I Have the Samsung s3c44b0x.
> > > I'd like use two timer in interrupt mode.
> > > So that i use the TIMER2 and the TIMER3 (use the
cyg_interrupt_create()).
> > >
> > > First step: run only the timer2 in fiq mode every 1ms. It works ok
> > > Second step: run only the timer3 in fiq mode every 2ms. It works ok
> > > Now: run timer2 in FIQ mode and the timer3 in IRQ mode. They work ok.
> > > But: if i run timer2 in FIQ mode and the timer3 in FIQ mode, they
don't
> > > work, and the system is lock.
> >
> > FIQ is not heavily used so i would not be supprised if there were a
> > few bugs remaining. Probably its a reentrance problem, ie handling a
> > second FIQ will still handling the first. Take a look at vectors.S and
> > see if you can find such a problem.
> >
>
> That is probably the case.
>
> It is good to keep in mind that FIQ support in vectors.S simply
> uses the same handling as a normal IRQ. There is no advantage to
> using an FIQ vs IRQ. The current code was intended to workaround
> poorly designed hardware which used the FIQ input for normal
> interrupts. Proper FIQ support would need to do something else.
>
> --Mark

I'd like use the FIQ vs IRQ because I don't want the variable time between
CPU 'signal' and the interrupt routine.
I check with the oscilloscope two signals: the CPU (CPU timer2 out toggle)
and a IO (PTF4).
In the FIQ mode, the time between these signal is constant (about 7us)
In the IRQ mode, the time between these signal is variable (from 7us to
150us)
This is a problem for my application. For this reason i choose the IRQ.
Now, Could I remove in the IRQ this variable time? Is it possible?
Thanks,
dS, MS.