Messages in this thread |  | | From | "Martin Eriksson" <> | Subject | Re: 'spurious 8259A interrupt: IRQ7' -> read the 8259 datasheet ! | Date | Fri, 30 Nov 2001 21:14:54 +0100 |
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----- Original Message ----- From: "Gunther Mayer" <Gunther.Mayer@t-online.de> To: <root@chaos.analogic.com> Cc: "Chris Meadors" <clubneon@hereintown.net>; "Martin Eriksson" <nitrax@giron.wox.org>; <linux-kernel@vger.kernel.org>; <martin@jtrix.com> Sent: Friday, November 30, 2001 8:28 PM Subject: Re: 'spurious 8259A interrupt: IRQ7' -> read the 8259 datasheet !
> "Richard B. Johnson" wrote: > > > > On Wed, 28 Nov 2001, Chris Meadors wrote: > > > > > On Wed, 28 Nov 2001, Martin Eriksson wrote: > > ... > ... rumours deleted (e.g. "printer status bits are all ORed into irq7") > ... > > >From "Harris Semiconductor 82C59A Interrupt Controller Datasheet": > If no interrupt request is present at step 4 of either sequence > (i.e., the request was too short in duration), the 82C59A will > issue an interrupt level 7.
Uhmm... call me slow, but I don't get it 100%... so this message has NOTHING to do with the LPT IRQ7? It just signals this because IRQ7 is the lowest priority IRQ on the 8259A?
> > 1. The irq controller sees an interrupt. > 2. The irq controller signals "there is _some_ interrupt" to the cpu. > 3. The CPU acks via INTA > 4. The irq controller looks if the irq is still there > (and signals IRQ7 if the line is no longer active).
Umm.. so again.. this means that the IRQ is not held long enough for the PIC to actually recognize *what* IRQ was asserted?
> > You have some device which doesn't keep the IRQ raised long enough ! > (or the CPU doesn't service the irq for a too long time and the > edge triggered irq is de-asserted or even serviced by a polling routine)
Thanks a bunch for clearing this up (this far)!!
When we get a firm indication on the 'problem', could the "spurious 8259A interrupt" message be de-obfuscated into something less unsettling?
PS. Real Men (tm) never reads the datasheets!
_____________________________________________________ | Martin Eriksson <nitrax@giron.wox.org> | MSc CSE student, department of Computing Science | Umeå University, Sweden
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