[LinuxBIOS] Geode GX1 system IRQ handling

Richard Smith smithbone at gmail.com
Wed Aug 16 22:01:44 CEST 2006

On 8/16/06, Jonathan Sturges <jsturges at speakeasy.net> wrote:

>  PCI: No IRQ known for interrupt pin A of device 00:13.0. Please try using
> pci=biosirq.
>  usb-ohci.c: found OHCI device with no IRQ assigned. check BIOS settings!
>  ...which basically means the entries for these devices in the IRQ map are
> either wrong, or missing.

This means that PCI interrupt A was aserted but was not routed to any
particular IRQ.

So then its very likely then that IntA is wired to the USB bridge.
Theres your first bit of routing info to try.  This and lspci gives
you most of the info you need.

Take the existing $PIR table and change it such that IntA is routed to
the IRQ of your choice ( an unused one is a good choice) and tell the
dirver to use that irq.

Now just because you have a irq table dosen't mean that the irq router
gets magically setup.  Depends on what the LinuxBIOS code does and
what Linux does. Linux in the past has not done a lot of the IRQ
routeing setup but its getting better all the time.

You will need to look at the datasheet for the IRQ router to see what
registers need to be dumped to see what PCI Int pins are routed to
wthat IRQ.

Richard A. Smith

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