[coreboot] Resource allocation

[Myles Watson]

> -----Original Message-----
> From: coreboot-bounces at coreboot.org [mailto:coreboot-bounces at coreboot.org]
> On Behalf Of Marc Jones
> Sent: Monday, November 10, 2008 3:28 PM
> To: Coreboot
> Subject: Re: [coreboot] Resource allocation
> 
> ----- Original Message ----
> > From: Myles Watson <mylesgw at gmail.com>
> > To: Coreboot <coreboot at coreboot.org>
> > Sent: Monday, November 10, 2008 2:53:57 PM
> > Subject: [coreboot] Resource allocation
> >
> > I need to clear up my understanding of resource allocation.  Here's my
> > understanding of it:
> >
> > 1. Start at the root with 2 resources (1 for memory, 1 for IO)
> > 2. For each child of each link:
> >     A. Add resources
> >     B. Get common constraints
> >     C. Descend links
> >     D. Propagate back to root
> >
> > When you're done you should have the Root device with the superset of
> all
> > devices' resources.
> >
> 
> Yes, and each bridge needs the resources grouped which is why the
> links(bridges) are desended as found.
> 
> > My question is if resources ever split.  In other words, lets imagine a
> > device which implements several IO ports in the 0x3fX range and larger
> > regions that must be mapped above 0x1000.  Since the limit for the
> smaller
> > regions is 0x7ff and the alignment for the larger regions is 0x1000,
> they
> > both can't coexist.
> >
> > What happens?
> 
> Everything
> below 0x1000 is legacy IO space and are not typically used by PCI
> devices (some devices/firmware sneek some stuff in around 0x800 for
> ACPI). As you noted there are some devices that might need to decode
> legacy regions to boot. If that is the case they will usually have a
> legacy enable bit in the header. In legacy mode the PCI BARs are
> ignored. The firmware, option ROM, and driver need to be aware of which
> mode it is in. An example is the AMD sb600 IDE controller(Device 20,
> Function 1). There is a legacy/PCI mode in the revision register ot
> offset 0x8.

Thanks Marc.

All right.  So the legacy IO resources shouldn't be grouped with the others.
Should they be marked Subtractive?  Are they declared to be special in a
different way?
 
Thanks,
Myles