[RFC] handle access to non-present IO ports on 8xx

[Mark Chambers]

> > >
> > > Hrm... removing a PCMCIA card triggers mchecks ? that is bad... With
> > > "proper" PCMCIA controllers, those are swallowed properly when the
card
> > > is removed. The eating of the machine check is a bit too hackish to my
> > > taste... Better is to "not do that" by making sure the legacy crap
isn't
> > > trying  to tap unexisting ports, but then, if PCMCIA is also a
> > > problem...
> >
> > Well, cardmgr calls the driver's shutdown/close routine as soon as
> > the card is removed. Some of those methods write to IO registers in
> > the process (eg net/pcmcia/pcnet_cs.c).
> >
> > I dont see any elegant change that could be done in PCMCIA.
>
> I know, the thing is, on platforms with a "classical" PCI<->PCMCIA
> bridge, the bridge will not issue machine checks when the card is
> removed. I don't know if that is possible with your HW setup, I suppose
> you are hooking PCMCIA directly to the CPU IO bus ...
>

I forget if I pointed this out already or not, but there's a good chance the
mchecks you are seeing are from a bad PCMCIA implementation, not
the 8xx itself.  PCMCIA uses WAIT, which is a negative ACK really,
and that must be pulled up externally, so if you remove the card any
active WAIT goes away.  I'd be glad to take a look at the schematics
if available and tell you if I think there might be a problem there.

Then again, maybe it doesn't matter where the mchecks are coming
from, you just need to handle them...

Mark Chambers