Re: [Qemu-devel] [PATCH 11/22] i8259: Update IRQ state after reset

[Avi Kivity]

----- Original Message -----
> On Sun, Oct 2, 2011 at 7:44 PM, Avi Kivity <address@hidden> wrote:
> >> >
> >> > A real device also ignores inputs during reset (or if it
> >> > doesn't,
> >> > we can just emulate that).
> >>
> >> Maybe this could work:
> >> 1 - issue start of reset cycle (raise qemu_irq, unrealize):
> >> internal
> >> states reset, no I/O.
> >> 2 - issue start of I/O, reset held (new phase): evaluate inputs
> >> and
> >> post outputs, but consider also that reset is still active, so
> >> transition is not complete for all devices
> >
> > This doesn't correspond to real hardware.   Each device detects the
> > reset edge independently.  There is no signal that says "all
> > devices have seen the edge".
>
> Reset is not edge triggered but level signal.

It still has propagation delay.  If your XNOR gate connects to the NORAD master 
launch controller, your design may have side effects.

>
> > We should either have just 1, or merge 1 and 2.
> >
>
> Then we'd be back to where the problems started.
>

Sorry, I don't see the problem yet.