linux-kernel - Re: question on odd APIC behavior

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Message-Id: <200711162234.54268.oliver@neukum.org>
Date:	Fri, 16 Nov 2007 22:34:53 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	"Maciej W. Rozycki" <macro@...ux-mips.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: question on odd APIC behavior

Am Freitag 16 November 2007 schrieb Maciej W. Rozycki:
> 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").

I am getting irq 19:nobody cared. Interrupts on 19 and 20 increase with
same rate, disconnecting the device on the bus stops the increase,
reconnecting it makes them increase again.

	Regards
		Oliver
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