Still IRQ routing problems with bridged devices.

John Baldwin jhb at
Fri Jan 2 11:20:30 PST 2004

On 01-Jan-2004 Bernd Walter wrote:
> On Thu, Jan 01, 2004 at 10:12:23AM -0700, M. Warner Losh wrote:
>> In message: <20040101155100.GF11668 at>
>>             Bernd Walter <ticso at> writes:
>> : On Wed, Dec 31, 2003 at 10:22:30PM -0700, M. Warner Losh wrote:
>> : > In message: <20040101013224.GC11668 at>
>> : >             Bernd Walter <ticso at> writes:
>> : > : The board is an old Asus T2P4 with 3 bridged cards and $PIR table.
>> : > : All IRQs behind bridges get bogusly IRQ4 instead of the right ones.
>> : > : Is this only a problem on some boards or do we have a general irq
>> : > : routing problem with bridges?
>> : > 
>> : > It is a problem with some bridges and PCI BIOS interrupt routing.
>> : 
>> : The intline registers are correct - that's what used to run since years.
>> : What has the kind of bridge to do with it?
>> just what the code does :-)
> But bridges are handled generic so why would only some bridges show
> this problem?
> The bridges are 21050 types btw.

Sounds like a BIOS bug.  If a bridge isn't listed in the $PIR, we
use the barber-pole swizzle to route across it.  However, that is
technically only defined for bridges on add-in cards.  The only
way we can tell if a bridge is on an add-in card is if it is not
listed either in ACPI's namespace with a _PRT or it is not listed
in the $PIR.  Part of teh problem is that we shouldn't be using
IRQ4 when we route PCI devices if you have IRQ4 used for an ISA
device anyway.


John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve!"  -

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