Gilles Chanteperdrix wrote:
> Sebastian Smolorz wrote:
> > Gilles Chanteperdrix wrote:
> >>Sebastian Smolorz wrote:
> >>>Hi,
> >>>
> >>>here's a proposal for a minor change in the I-pipe implementation for
> >>>ARM. Since it is required for my S3C24xx patch not to call
> >>>__ipipe_mach_set_dec directly when the timer is released by the Xenomai
> >>>domain I suggest the following changes. The patch comprises the
> >>> necessary modifications for PXA, SA1100 and Integrator, too.
> >>>
> >>>Comments or objections?
> >>
> >>Why can not you call __ipipe_mach_set_dec directly when the timer is
> >>released ?
> >
> > The timer used for generating interrupts operates in auto-reloading mode
> > when it is under Linux control. But when Xenomai reloads the timer the
> > mode of operation is one-shot (auto-reload feature in hardware is off).
> > So I have to make a distinction between setting the dec value by Xenomai
> > for programming the next period and setting the dec value to
> > __ipipe_mach_ticks_per_jiffy when the timer control is given back to
> > Linux.
> >
> > The reason for this is the fact that programming a timer on the S3C24xx
> > can take some ticks which means that these ticks aren't count whereas
> > time is going on in the real world. So it is more reasonable to let the
> > timer reload itself when Xenomai hasn't started it. Setting
> > __ipipe_mach_ticks_per_jiffy in the Linux interrupt handler would make
> > every period last some ticks longer.
>
> You can avoid this problem by adding LATCH or
> __ipipe_mach_ticks_per_jiffy to the current value of the match register
> in the timer interrupt, as it is done for the SA and PXA architectures.

Unfortunately, this solution is not applicable. The timers of PXA and SA are 
counting up whereas the S3C24xx timers are counting down to zero. There is no 
match register for the next interrupt. In contrast, the timer must be 
programmed with the new dec value directly, thus stopping it for the time of 
re-programming.

--
Sebastian

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