From owner-freebsd-hackers  Wed Sep 25 11:08:05 1996
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.5/8.7.3) id LAA17308
          for hackers-outgoing; Wed, 25 Sep 1996 11:08:05 -0700 (PDT)
Received: from Octopussy (Octopussy.MI.Uni-Koeln.DE [134.95.212.20])
          by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id LAA16342
          for <freebsd-hackers@freebsd.org>; Wed, 25 Sep 1996 11:06:42 -0700 (PDT)
Received: from x14.mi.uni-koeln.de (annexr2-47.slip.Uni-Koeln.DE) by Octopussy with SMTP id AA05467
  (5.67b/IDA-1.5 for <freebsd-hackers@freebsd.org>); Wed, 25 Sep 1996 20:06:37 +0200
Received: (from se@localhost) by x14.mi.uni-koeln.de (8.7.6/8.6.9) id UAA18578; Wed, 25 Sep 1996 20:06:25 +0200 (MET DST)
Date: Wed, 25 Sep 1996 20:06:25 +0200 (MET DST)
Message-Id: <199609251806.UAA18578@x14.mi.uni-koeln.de>
From: Stefan Esser <se@zpr.uni-koeln.de>
To: Bruce Evans <bde@zeta.org.au>
Cc: durian@plutotech.com, freebsd-hackers@freebsd.org
Subject: Re: Special Cycles on the PCI bus
In-Reply-To: <199609240742.RAA22722@godzilla.zeta.org.au>
References: <199609240742.RAA22722@godzilla.zeta.org.au>
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

Bruce Evans writes:
 > >Now's the interresting bit - notice the high bits (0xFC)
 > >in the write/read address.  They can't be intentional.  I also find
 > >it interesting that the accesses to FCA0 are full 32 bit writes.
 > >
 > >	I/O WRITE ADR=0000FC87
 > >		D32=06xxxxxx
 > >	I/O READ ADR=0000FC87
 > >		D32=06xxxxxx
 > >	I/O WRITE ADR=0000FC90
 > >		D32=xxxxxx00
 > >	I/O READ ADR=0000FC90
 > >		D32=xxxxxx00

 > No, this seems reasonable.  isa/pcibus.c does 32-bit accesses to port
 > 0xc000 | (device << 8ul).

Well, but those are only used for config space accesses,
and config space is normally not touched at all, after 
the PCI probe and attach are complete.

But depending on the chip set model, the special cycles
may actually be requested by writing into those chip set
registers, that are normally used to address config space.

I'd need to know more about the system configuration (boot 
messages and the driver that causes the special cycles) 
and will then try to understand what's going on ...

Regards, STefan