[9217] in linux-scsi channel archive
sym53c8xx: edge/level trigged IRQ: solved [was: Re: Feature in ncr53c8xx/sym53c8xx driver]
daemon@ATHENA.MIT.EDU (Miquel van Smoorenburg)
Mon Jul 17 07:24:52 2000
Date: Mon, 17 Jul 2000 13:23:02 +0200
From: Miquel van Smoorenburg <miquels@cistron.nl>
To: =?iso-8859-1?Q?G=E9rard_Roudier?= <groudier@club-internet.fr>
Cc: linux-scsi@vger.rutgers.edu
Message-ID: <20000717132302.A7132@cistron.nl>
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In-Reply-To: <Pine.LNX.4.10.10007141856130.1674-100000@linux.local>; from groudier@club-internet.fr on Fri, Jul 14, 2000 at 07:04:31PM +0200
According to Gérard Roudier:
> On Fri, 14 Jul 2000, Miquel van Smoorenburg wrote:
> > According to Gérard Roudier:
> > > PCI interrupt lines are REQUIRED be configured for LEVEL SENSITIVE.
> > >
> > I suspected something like that, but in the AMI bios there is no way
> > I can change those settings. Neither in the main setup or in the
> > SCSI BIOS setup. It's simply how the AMI board sets itself up.
> > (AMI Megarum II board, BIOS release 774-031400 i.e. the latest).
> >
> > Do you know of any way to fix that ? Perhaps a bug in the APIC
> > setup in the kernel, or a bug in the board itself?
>
> I am not this SMP aware :), but the BIOS has just to be right about the
> BUS type that owns the IRQ and the kernel will configure the IO_APIC for
> level-sensitive for this IRQ and will handle the IRQ as level-sensitive if
> BUS is PCI type. Looks like the MP table is being wrong about the BUS for
> the IRQ assigned to the SYMBIOS chip, but I cannot be 100% sure of that.
Yes, this appeared to be the case - a bug in the BIOS, where the IRQ
is reported as edge while it in reality is level
> You will get better help from the linux-kernel or linux-smp list, in my
> opinion.
I spent some more time searching with Google based on this new information,
and I found a message from Jos van de Ven on the linux-smp list with a
small patch to arch/i386/kernel/io_apic.c that makes it possible to override
the BIOS information with a command line option (ioapic_level=10,15).
With that patch, the system runs just fine, even with the stock
symbios drivers in 2.2.x
See http://marc.theaimsgroup.com/?l=linux-smp&m=93143486926833&w=2
I've mailed Jos to ask if he intends to polish it up and send it
to Alan/Linus for inclusion in 2.2.18 and/or 2.4.
Thanks for all the help,
Mike.
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