Re: [OpenBIOS] sun4u interrupt-map

[Blue Swirl]

On Wed, Apr 4, 2012 at 20:15, Artyom Tarasenko  wrote:
> On Wed, Apr 4, 2012 at 9:58 PM, Blue Swirl  wrote:
> > On Wed, Apr 4, 2012 at 17:59, Tarl Neustaedter  wrote:
> > > On 2012-Apr-4 13:30 , Artyom Tarasenko wrote:
> > > > Could it be that OpenBIOS is missing interrupt-map and
> > > > interrupt-map-mask properties for the PCI bus?
> > > >
> > > > On a real Ultra-5 it looks like this:
> > > > interrupt-map            0000003c 00000000 00000000 f005fa24 80000033
> > > > interrupt-map-mask       0000003e 00000000 00000000
> > > >
> > > > What is mapped to what?
> > > >
> > > > I couldn't find any documentation how these properties work, except
> > > > for Linux and OpenSolaris sources. Thought I ask here before trying to
> > > > reconstruct the picture from them.
> > >
> > > These are documented at least as far back as the Safari binding, in section
> > > 5.2.1.4 (assuming that spec got published). They are used to route
> > > interrupts differently than the data interconnects for devices -
> > > specifically, when hardware has taken the interrupt pins from a device and
> > > brought them in to the CPU through a path which bypasses all the intervening
> > > bridges. The specification for interrupt-map is:
> > >
> > > child.hi child.mid child.lo child.intrspec intr-parent.phandle
> > > intr-parent.intrspec
> > >
> > > Basically, it defines the child, the child's interrupt then points to the
> > > parent where the interrupt appears and what interrupt it appears as. In the
> > > above Ultra-5 spec, it looks like the first three cells are defining the
> > > child (3c?), and the interrupt from that child (presumably zero), saying
> > > that this interrupt appears under node f005fa24 as interrupt 33.
>
> So, basically, without these properties, software would have no way to
> tell what CPU interrupt is pulled when the device irq becomes active,
> right?
> > > The interrupt-map-mask is simply a mask applied to the child information
> > > it's defined as
> > >
> > > child.hi child.mid child.lo child.intrspec
> > >
> > > Evidently on the Ultra-5, we aren't using three cells to identify the child,
> > > only two. So we probably skip child.mid in both of the above specifications.
> >
> > Nice explanation. I read the Open Firmware draft interrupt mapping
> > document (http://www.openfirmware.org/1275/practice/imap/imap0_9d.pdf),
> > but I was more confused after reading it than before.
>
> Hm. Since it's a part of a standard specification, the other machines
> (i.e. PPC) might need these properties as well?

Probably. There used to be PPC OF device tree dumps in this site but
it's no longer there:
http://penguinppc.org/historical/dev-trees-html/
> Artyom
>
> solaris/sparc under qemu blog: http://tyom.blogspot.com/search/label/qemu