[OpenBIOS] sun4u interrupt-map

Blue Swirl blauwirbel at gmail.com
Wed Apr 4 21:58:02 CEST 2012

On Wed, Apr 4, 2012 at 17:59, Tarl Neustaedter <tarl-b2 at tarl.net> 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
> (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.
> 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.

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