linux-kernel - Re: question on odd APIC behavior

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Date:	Fri, 16 Nov 2007 11:20:51 +0000 (GMT)
From:	"Maciej W. Rozycki" <macro@...ux-mips.org>
To:	Oliver Neukum <oliver@...kum.org>
cc:	linux-kernel@...r.kernel.org
Subject: Re: question on odd APIC behavior

On Fri, 16 Nov 2007, Oliver Neukum wrote:

> > > On irq 20, there's an UHCI, on irq 19 is an EHCI. For every interrupt on 20
> > > there's a spurious interrupt on 19. USB devices on bus of the controller on 20
> > > work. So I know all interrupts are seen. ERR does not increase. Interrupts
> > > for devices on the bus of the controller on 19 arrive at 19 only.
> > 
> >  I suggest you try to sort it out with the maintainers of the UHCI and 
> > EHCI drivers then.
> 
> They are innocent. This laptop really delivers an interrupt twice.

 Perhaps, but these drivers are involved and the device-specific knowledge 
will help tracking down the cause.  I have general experience on how 
interrupts work, including on APIC-based systems, but I have no idea how 
UHCI and EHCI devices work in this area and, in particular, how you know 
an interrupt coming from the line #19 is related to one on the line #20 
and then a spurious one if not recorded as ERR or otherwise unclaimed 
(which would be reported as "irq 19: nobody cared").

  Maciej
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