Re: [PATCH 8/8] q800: add NMI handler

[Mark Cave-Ayland]

On 15/10/2021 09:40, Laurent Vivier wrote:

> Le 13/10/2021 à 23:21, Mark Cave-Ayland a écrit :
> > This allows the programmer's switch to be triggered via the monitor for 
> > debugging
> > purposes. Since the CPU level 7 interrupt is level-triggered, use a timer to 
> > hold
> > the NMI active for 100ms before releasing it again.
>
> I'm wondering if Qemu provides another way to have a level-triggered interrupt 
> in this case.
>
> I' tried to see if keeping the button pressed on a mac kept the IRQ up (as QMP 
> NMI does), but a real
> mac is too slow and has to many things to display it was not really 
> conclusive...

When writing the patch I rebased the outstanding MacOS patches onto the branch, 
installed Macsbug into MacOS and used "info nmi" to break into it.

Testing glue_nmi() with:

  GLUE_set_irq(s, GLUE_IRQ_IN_NMI, 1);
  GLUE_set_irq(s, GLUE_IRQ_IN_NMI, 0);

i.e. a simple pulse didn't launch MacsBug at all. Keeping the NMI high launches 
MacsBug (which is usable) but then as soon as you exit MacsBug with ES, MacsBug 
breaks immediately again making it impossible to return to the Finder. Adding the 
timer allows launching MacsBug and then exiting/re-entering MacsBug again on demand 
as expected.


ATB,

Mark.