linux-kernel - Re: Syba 8-Port Serial Card Unidentified By Kernel

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Message-ID: <20071026113544.GA20216@pazke.donpac.ru>
Date:	Fri, 26 Oct 2007 15:35:45 +0400
From:	Andrey Panin <pazke@...pac.ru>
To:	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>
Cc:	Chris Bergeron <chris@...urn.com>, linux-kernel@...r.kernel.org
Subject: Re: Syba 8-Port Serial Card Unidentified By Kernel

On 295, 10 22, 2007 at 12:18:08PM -0400, Lennart Sorensen wrote:
> On Mon, Oct 22, 2007 at 07:33:23PM +0400, Andrey Panin wrote:
> > So the card probably generates screaming interrupt... that's bad.
> > I found some docs for IT887x chips, according to these docs  IT887x
> > have simple interrupt controller inside. Further investigation is needed.
> > 
> > Can you post output of lspci -xxx ?
> 
> Is it possible they put a chip on to generate a PCI interrupt on perhaps
> PCIB on the slot from the serial chips directly, so that they didn't
> have to turn interrupts from the serial chips into a signal that forces
> the parallel port to generate an interrupt?  After all that would reduce
> latency, and if you use PCIA for the parallel port, PCIB for the first
> serial chip and PCIC for the second, you might get a much more efficient
> design, although the driver would have to register all those IRQs.

I dont think so. IT887x has builtin interrupt controller which multiplexes 
16 external IRQ pins with IRQs from builtin devices (parallel port, UARTs
and GPIO) into single INTA# line. IT887x also contains 8-bit ISA-like bus
and 16 chip select lines and it's all you need to glue UARTs to PCI bus.

I suspect that it's interrupt controller problem, probably edge/level
triggered settings.

> What IRQ is each PCI device in that system using right now?  perhaps we
> could figure out what irq 17 would be on that PCI slot.

-- 
Andrey Panin		| Linux and UNIX system administrator
pazke@...pac.ru		| PGP key: wwwkeys.pgp.net

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