IRQ Question?

[Wilkinson, Alex]

    0n Wed, Apr 18, 2007 at 07:26:35PM -0700, Nate Lawson wrote: 

    >> FreeBSD 7.0-CURRENT #0: Tue Apr 10 13:47:53 WST 2007
    >> 
    >> Could be an insanely dumb question, however, I have to ask.
    >> 
    >> Why don't IRQs in the BIOS map to IRQs in the output of vmstat(8) ?
    >> 
    >> e.g.
    >> 
    >> I manually changed an IRQ assingment of an Intel NIC [em(4)] to be on IRQ 11 in
    >> the BIOS and vmstat(8) reports its as irq16.
    >> 
    >>   #vmstat -i | egrep -i em
    >>    irq16: em0 uhci0  2990236  18
    >> 
    >> Can someone (njl@ jhb@) please enlighten me ?
    >
    >Interrupt routing is determined by a number of factors.  Without acpi,
    >it's determined by the BIOS initial irq and then anything the $PIR table
    >changes (usually matches the BIOS value).  With acpi, it's the BIOS irq
    >and MADT acpi table.  And that assumes APIC, not PIC-based routing.
    >
    >You can override the values with these tunables from the acpi man page:
    >
    >     hw.pci.link.%s.%d.irq
    >       Override the interrupt to use for this link and index.  This
    >       capability should be used carefully, and only if a device is not
    >       working with acpi enabled.  "%s" is the name of the link (e.g.,
    >       LNKA).  "%d" is the resource index when the link supports multi-
    >       ple IRQs.  Most PCI links only have one IRQ resource, so the
    >       below form should be used.
    >
    >     hw.pci.link.%s.irq
    >       Override the interrupt to use.  This capability should be used
    >       carefully, and only if a device is not working with acpi enabled.
    >       "%s" is the name of the link (e.g., LNKA).
    >
    >You'll have to look at your dmesg to determine the proper values here.

Cheers Nate !

 -aW

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