Re: RPXLite 823 PCMCIA troubles

[Brian Kuschak <bkuschak@yahoo.com>]

Mark,

One thing to note about PCMCIA I/O region accesses on
the 823...

If the access is to a 16-bit port, the PCMCIA
controller needs to see an acknowledgement from the
card on the IOIS16_B pin.  However when the processor
is configured for debugging (full trace, etc) this pin
is unavailable.  It's muxed with some other debug
function (VFLS, I think?).  Check your settings in the
SIUMCR register.  If the core never gets this
acknowledge on the 16 bit access, it might generate a
bus error, which would show up as a machine check.

There are only two solutions for this hardware
shortcoming.  Either setup the SIUMCR to give up your
trace capability (which isn't very useful w/ virtual
memory anyway), or don't do 16-bit accesses in PCMCIA
I/O space.

Hope that helps.
-Brian Kuschak


--- "Mark S. Mathews" <mark@absoval.com> wrote:
> 
> Howdy Folks,
> 
> Ok, the wlan PCMCIA card is working....but only
> after an ugly hack.
> Basically, I modified
> the MachineCheck function to ignore the exception
> (just return) if the
> faulting address (contents of DAR) falls in the
> iomapped range we've
> established for the PCMCIA card.
> 
> Any opinions on our solution?
> 
> I'd still like to know what's causing these
> exceptions, but that's for
> another day.
> 
> -Mark
> 
> On Tue, 30 Nov 1999, Dan Malek wrote:
> 
> > 
> > Mark S. Mathews wrote:
> > 
> > 
> > > Hmmmm.  The way ours "works for awhile", I'm
> wondering if there's a
> > > problem w/ the way the 8xx is handling the WAIT#
> when the MMU is enabled
> > > (?)
> > 
> > Shouldn't be the problem.  The MMU appears (on
> block diagrams
> > anyway :-) to be far enough removed from the
> memory controller
> > for this to happen.
> > 
> > 
> > > This is good to know.  Our card supports I/O or
> memory access to the
> > > shared memory.  We'll shift over to the I/O and
> try that.
> > 
> > The version I have running on my PowerBook only
> uses I/O.....
> > or am I mistaken?
> > 
> > 
> > > We've been running _lots_ of experiments with
> the timing settings.  So far
> > > 3,10,6 seems to work best....but it still fails.
> > 
> > Thanks.  I'll keep those numbers around.....there
> are others
> > I would rather see.....:-).
> > 
> > 
> > > I've seen the 'guarded' thing around in the
> sources, but I'm not sure what
> > > it's all about.  Guess I should look. ;-)
> > 
> > I just fixed it.  I'll send it to you privately as
> well as
> > post it on the ppc.kernel.org server.  I hope it
> corrects
> > something.
> > 
> > 
> > 
> > 	-- Dan
> > 
> 
> 
> Mark S. Mathews
> 
> AbsoluteValue Software     Web:   
> http://www.absoval.com
> P.O. Box 941149            e-mail: mark@absoval.com
> Maitland, FL 32794-1149    Phone:  407.644.8582
> USA                        Fax:    407.539.1294
> 
> 
> 


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