[coreboot] v3: dts and arrays

Corey Osgood corey.osgood at gmail.com
Fri Feb 15 01:15:34 CET 2008

On Thu, Feb 14, 2008 at 6:35 PM, Tom Sylla <tsylla at gmail.com> wrote:

> ron minnich wrote:
> > On Thu, Feb 14, 2008 at 2:32 PM, Carl-Daniel Hailfinger
> >>  Indeed. That would solve the problem very nicely without putting hacks
> >>  into the dts.
> >>
> >
> > OK, so we put nodes under the 5536, and specify 'disabled', and the
> > 5536 code knows to actually call VSA when it sees that they are
> > disabled. This is nice. It would use the device tree in a sensible
> > way.
> Hm, hold on. I think there is a little bit of confusion with the word
> "disabled" here. For a Geode VPCI device, "disabling" it means
> completely hiding the header from config space. If you "disable" it with
> VPCI, and try to do config cycles to that device, VSA will respond as if
> it does not exist. (returning all 1's) That behavior continues forever,
> unless you "enable" the device again using VSA. (you wouldn't ever do
> that, in general)
> What does "disabled" mean for a real hardware device in the dts? I am
> pretty sure it does not mean "hide the header" (that is not possible in
> general, it is a VSA-ism).
> What if I want the VPCI device to exist, but want it "disabled" in the
> normal dts sense of "disable"? Overloading "disabled" in the dts makes
> that not possible (and is also *really* confusing)
> Maybe a better idea would be to just change:
> /* Disable unwanted virtualized PCI devices */
> to
> /* Hide headers for unwanted virtualized PCI devices */
> since the original words seem to have lead to this confusion.

Keeping in mind that I'm no expert or really even informed with the v3/dts
internals or Geode, but similar behavior is seen on the intel ICH-series and
via vt8237r, would it work to add another option, call it "hidden", to the
device status, and then another stage to v3? We'd do whatever stage scans
the pci bridge to find all the devices, then whatever devices are marked
hidden have whatever mechanism that hides them run, and v3 "forgets" the
devices ever existed. i82801xx (ICH) in v2 already works to hide these
devices, but I can't really remember how it works. This is just a general
idea, I figure you guys have a much better idea then I do if it'd work/be
possible or not.

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