On Mon, Sep 11, 2006 at 02:44:27PM -0700, Tim Rightnour wrote:
> On 11-Sep-2006 Cory Bajus wrote:
> > I don't think slots 1&2 are on a secondary bus.  According to the
> > IBM docs, slots 1-3 are in a primary bus and 4-9 are on a secondary
> > bus (i.e. behind a ppb).  The 7043-140 is similar, with slots 1&2
> > primary and 3-5 secondary.  What makes slots 1&2 unique on F40's is
> > that they are 64-bit slots - do these need to be treated differently
> > by NetBSD?
> 
> According to the residual data: 
> http://www.garbled.net/tmp/residual/residual.7025-F40
> 
> There are three complete PCI bridges on the machine.  When scanning the primary
> host bridge, you see the pci-pci bridge on there.  However, even scanning both
> bridges, we never see the third bridge.  Given the fact that they number the
> bridge 128, and give a parent locator of 0 (supposedly meaning it's
> cpu-attached) I suspect this third bridge is actually a second host bridge.  So
> what I think this machine needs is:
> 
> pci0 at mainbus
> ppb0 at pci0
> pci1 at ppb0
> pci2 at mainbus

OK, this makes sense.  I was confused by the description of the missing
bus as a secondary bus - in IBM-speak a 'secondary' bus is always behind
a PCI-PCI bridge.

> Complications arise here, because the second primary bus seems to have a
> different base address than the primary bus, (which makes sense actually).  So
> I need to rewrite some of the attachment code in mainbus I believe.
> 
> Note that in the residual, "Pci Slot 3" is noted as being under the primary
> bus, (DEVICE 2) and slots 1 and 2 are under this third, wierd bus.  The bridge
> is listed as having slots 4-9.
> 
> Given that you say they are 64 bit slots.. it wouldn't surprise me at all if
> IBM put a second primary bus in the machine to make them run extra-fast.

That looks to be the case.  Multiple primary buses are very common in the
newer CHRP systems as well (although I didn't realize the F40 had two
primary buses).

> I'd like to see the IBM docs you spoke of..  do you have a part number for the
> book, or have it in PDF form?

The IBM doc is the old RS/6000 'PCI Adapter Placement Guide'.  It doesn't
have any useful technical info for probing the buses; it just shows the
slot layout (primary/secondary, width, speed, voltage, etc.) for the various
PCI-based RS/6000 models.