Re: [Adeos-main] interrupt latency

[Philippe Gerum <rpm@xenomai.org>]

On Mon, 2004-02-23 at 03:22, Dirk Roloff wrote:
> Am Montag, 23. Februar 2004 00:52 schrieb Philippe Gerum:
> > On Mon, 2004-02-23 at 00:35, Dirk Roloff wrote:
> > > Hi List,
> > >
> > > I ve got the following problem:
> > >
> > > I have to write a driver for linux for a receiver-board.
> --- schnipp ---- 
> >
> > It would be interesting to know the flags passed to
> > adeos_virtualize_irq(). In any case, either the 4th arg should pass
> > IPIPE_PASS_MASK, or you realtime_handler() routine should call
> > adeos_propagate_irq(irq).
> Philippe:
> 
> the exactly code is:
>       if( 0 != adeos_virtualize_irq( irq[i], &rt_amcc_irq_handler, NULL, 
> IPIPE_PASS_MASK | IPIPE_HANDLE_MASK) )
> 
> i want to handle and pass it down the pipe.
> 
> But i give propagate a try ... not realy better ... 

> Now a second IRQ 4 will be delivert to the linux handler.


That's normal. Either set IPIPE_PASS_MASK if you want Adeos to propagate
the incoming IRQ unconditionally, _or_ don't set it if you want your
handler to decide dynamically of whether the propagation should take
place or not on a per-IRQ basis using adeos_propagate_irq().

> Only one IRQ 1 to the realtime (its masked out in PIC  when entering the 
> realtime)

That's ok too. By default on the x86 port, IRQs are mask & acked upon
receipt before the IRQ flows down the pipeline, except the 8254 timer
which is only acked.

> Could it be that this will block all other IRQ at PIC level ?
> 

Here are the typical actions taken upon IRQ receipt with a single
prioritary domain running above Linux in the pipeline:

hw IRQ =>
	[Adeos primary handler]
		=> mask and ack (from now, IRQ is masked at 8259 level)
		=> pipeline walk (all pending IRQs)
			=> realtime_handler(irq)
				[Your processing]
				adeos_propagate_irq(irq) (unless you set 						              
IPIPE_PASS_MASK)
			=> Linux handler()
				[Linux's do_IRQ(irq)]
				end_irq() (which re-enables the IRQ 					    line at the 8259 level)

If you want to re-enable the IRQ line earlier in the process (i.e.
before Linux's regular handler is run), then you can do this by calling
adeos_control_irq(irq,0,IPIPE_ENABLE_MASK) in your real-time handler. 

You may want to have a look at the Adeos CVS, under linux/examples:
there are a set of testing and measurement programs illustrating how the
pipeline shall be controlled.

Btw: which Adeos version are you using? 

> Dirk.
> 
> 
> 
> 
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-- 

Philippe.