BIOS interrupt configuration

[ABIVEN Anne <ABIVEN@crf.canon.fr>]

Hello,

We have some troubles related to PCI interrupts on our board. On our board 
we have the Intel Triton 82430HX and 82371 PIIX3 controllers.This board is 
running a BIOS designed for this chipset. On this board we have  PCI devices 
which have one interrupt Int A. For some devices, this interrupt is cabled 
on our PCI bus on another line, int D for exemple, this seems to be 
authorized by the PCI revision 2.1, see page 14.
During the configuration stage, the BIOS configures the PIIX3 to route the 
PCI interrupts. Thanks to the PCI analyser I can see what is written in the 
PIIX3 controller ( register PIRQC[A:D] offset 60-63h in the config space 
function 0) . So
int A is routed to irq 11
int B is routed to irq  10
int C is routed to irq  4
int D is routed to irq  9

I also have a look at the header of my PCI devices. One of the device which 
int A is cabled to int A of the bus should have at offset 3C of the 
configuration space the value 11 for its interrupt line, to be in accordance 
with the programmation of the PIIX3. But the value written and read is 10, 
as if its interrupt pin was B.
An other device which intA is cabled to int D has 11 as interrupt line, I 
think it should be 9 according to the PIIX3.


When we use the routing facility described on page 14 of the spec, that is 
int A of one device cabled to int D for instance, how can the BIOS know this 
as, in the configuration header, the interrupt pin is A. In our case it is 
strange because if the BIOS relies on the interrupt pin, it should write 11 
and not 10 in the interrupt line for the device with intA connected to intA 
of the bus. So the fact that the interrupts can be re-routed (intA connected 
to intD.....) may be a problem but not the only one.

So, if the OS reads the configuration space of each PCI device, it does not 
get the right interrupt line and can not run.It must know the hardware 
configuration of the board and read the PIIX3 register to get the interrupt 
line. This is not what is usually done by most OS (linux for example). So 
what is wrong ?
Is it the BIOS or is it the board design ?

Any help would be appreciated.

Thank you

Anne

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