[coreboot] Creating PIRQ table

[Gergely Kiss]

Hi All,

my name is Gergely Kiss and I'm currently working on porting Coreboot to
the ASUS AM1I-A board.

I'm a great fan of open source software, I've contributed a few times to
some well-known projects like Squid, Monodevelop and Openwrt, just to name
a few.

I would need a little bit of help from the devs about how to create the PCI
IRQ routing table for my board (the easiest way possible).

I'm using the Biostar AM1ML board as a template as it looks to be a very
similar board as the one I have. The only differences I can see is the
SuperIO (ITE 8623E) & the audio chip (Realtek ALC887-VD) and also some
minor things with the board layout so I'm not expecting to have too much
difficulties.

Looking at the file
https://review.coreboot.org/cgit/coreboot.git/tree/src/mainboard/biostar/am1ml/irq_tables.c,
the following questions came to my mind:

* Do I really have to follow the "long way" as outlined in the Wiki page at
https://www.coreboot.org/Creating_Valid_IRQ_Tables? Couldn't I just fetch
the routing table from the OEM BIOS somehow and implement it in the source?
* What's the meaning of the fields "link" & "bitmap"? Are these common for
all boards with the same chipset? Where should I look up this information?
* I believe I have to create as many entries within the struct as many IRQ
slots exist for the board. Am I right?

I found a table in the board's manual (attached) which looks useful but I'm
afraid it might not contain all the information I need to construct a valid
routing table.

As for the SuperIO chip, I think I won't have too much issues getting it to
work as it looks like ITE SIO chips are quite similar from the developer's
perspective but I still miss having a datasheet available. I'll try to
reach out to the vendor to see if they are willing to share a datasheet
with me.

Any help from you guys is much appreciated.

Thanks & Regards,
Gergely
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