[coreboot] IRQ 9 on s2895 and s2892

Rudolf Marek r.marek at assembler.cz
Wed Mar 11 00:06:26 CET 2009

> I'm extracting this from a different thread hoping for more help :)

> How do you find an interrupt source that's going crazy like that?
> When I boot with acpi=off I IRQ9 doesn't even get registered.

This matches whats going on. The shared IRQ handler for IRQ9 looks to all 
functions which has registered via request_irq. Each such function returns 
IRQ_HANDLED or IRQ_NONE when it detects its not their iRQ.

To get a source look to:

1) superIO config
2) PCI IRQ router inside SB (it is used to route the IRQ to 8259, its just a bit 
more complex multiplexor which decides if IRQ goes to APIC or 8259 or both.

I cannot find anything about nvidia IRQ routers :/ I hate no-docs state!

3) by observation
    a) boot kernel with initramfs filesystem (or initrd)
    b) mount /proc/
    c) observe if any activity is on that IRQ
    d) if not load some drivers for PCI devices (network etc...)
    e) or even better try without ethernet plugged, USB...

Or better method is to hack the "disabling IRQ" handler and printk the interrupt 
counter there to see if it matches some other count.


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