Re: VIA KT400 + Kernel 2.6.12 + IO-APIC + uhci_hcd = IRQ trouble

From: Alan Stern
Date: Mon Jul 25 2005 - 21:04:21 EST

On Tue, 26 Jul 2005, Michel Bouissou wrote:

> Le Lundi 25 Juillet 2005 22:44, Alan Stern a écrit :
> >
> > Now that's strange.  When you plug the high-speed device into the
> > integrated ports, which IRQ counter changes?  Since nothing is using IRQ
> > 21, it should be disabled and its counter should remain constant.  Does
> > this mean the interrupts show up on IRQ 19 (used by ehci-hcd), or do they
> > not show up at all (i.e., is the USB connection just being polled)?
> I assume it's IRQ 19.
> cat /proc/interrupts doesn't show IRQ21 at all when uhci isn't loaded.

As it shouldn't, since nothing is supposed to be using that IRQ.

> IRQ 19 being shared with 4 IDE controllers that controls my hard drives,
> that's hard to isolate interrupts counts due to USB activity from interrupts
> counts due to disks activity...

I was afraid you'd say that...

Natalie, that's all I can think of. Now it's up to you to invent a patch
Michel can try out, to show just where the IO-APIC code is going wrong.

Alan Stern

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