Early PCI auto-configuration
Mark A. Greer
mgreer at mvista.com
Fri Oct 27 09:46:35 EST 2000
[The discussion below is based on the latest fsmlabs 5005 repository
Disclaimer: I'm fairly new to linux PPC so my apologies if this has been
My problem: The firmware on a couple platform I need to support do
absolutely _no_ PCI device initialization.
To make things work for these boards in the current setup, I need to use
one of the pcibios_fixup() or pcibios_fixup_bus() hooks to walk the
entire bus tree, setup the devices (including bridges), and sort out all
the stuff that's already been put in the the "resource" entries--or am I
I would prefer to run a "pci auto-configurator" that sets up all the
devices and bridges before pci_init() runs so I don't waste as much time
reading bad info and they trying to fix it all up later. The "fixup"
routines can still be used for minor tweaks and interrupt routing, etc.
I was thinking of doing it this ways...
>From the xxx_find_bridges() routine, call "pci_auto_scan_hose()" which
walks the entire bus hierarchy under each "hose" sorting out resources,
enumerating the buses, setting up bridges and their bounds, etc.
pci_init() will run some time later and pick up reasonable BAR values.
To make this work, I will add 4 fields to the pci_controller [or "hose"]
structure that have the upper and lower bounds for PCI I/O and memory
space for each hose. This is what the auto-configurator will use to
constrain his resource allocations.
Also, while I'm at it, add 2 more fields to pci_controller, one an array
of 32*8 int's that contian the devfn value of any devfn's that the
auto-configurator should skip. The other is the number of valid entries
in the array. This is useful--to me anyway--because I want the
auto-configurator to skip the host bridge itself. Also, on some
platforms, the host bridge also has an external IDSEL line that is
hooked up to a PCI address line. Some bridges can not handle having
themselves selected so that device needs to be skipped.
Any comments? Is there a better way? Am I getting carried away?
Mark A. Greer (mgreer at mvista.com; 480-517-0287)
MontaVista Software, Inc.
2141 E. Broadway Road, Suite 108
Tempe, AZ 85282
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