[OpenBIOS] sun4u interrupt-map

Tarl Neustaedter tarl-b2 at tarl.net
Wed Apr 4 19:59:51 CEST 2012

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 

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 

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