Re: 2.6.2-rc3: irq#19 - nobody cared - with an au88xx

[Jeff Garzik]

Daniel Jacobowitz wrote:
> On Mon, Apr 12, 2004 at 02:51:47PM -0400, Daniel Jacobowitz wrote:
>
> > [Jeff, I'm sending this to you because your name is above the Via PCI
> > quirks.  It's in a followup comment, though, so there's probably
> > someone else I should be talking to about the original quirks - I just
> > haven't worked out who yet.]
> >
> > I'm trying to track down an interrupt routing problem on my Via-chipset
> > motherboard (it's an Abit VP6).  The symptoms are that the USB and
> > audio drivers eat each other; it appears that they are on the same
> > IRQ line, even though /proc/interrupts says:
> > 11:     300000          0   IO-APIC-level  uhci_hcd, uhci_hcd
> > 19:     299999          1   IO-APIC-level  au8830
> >
> > So eventually one of them gets wedged on, and the other panics because
> > it can't identify the incoming interrupts.
> >
> > At boot I see this, from drivers/pci/quirks.c:
> >
> > PCI: Via IRQ fixup for 0000:00:07.2, from 5 to 11
> > PCI: Via IRQ fixup for 0000:00:07.3, from 5 to 11
> >
> > Is it possible that the same problem, i.e. writes to the INTERRUPT_LINE
> > register causing connection to the PIC, could apply to devices in the PCI
> > slots?  The register still shows 5 for the au8830, which is the IRQ it
> > gets assigned to if I boot without ACPI.
> >
> > I know this hypothesis sounds a little weak.  I'm running out of ideas
> > :)
>
>
> I've worked out the part of the problem involving that quirk.  There's
> an entry in quirks.c which reads:
>
> /*
>  *      VIA northbridges care about PCI_INTERRUPT_LINE
>  */
>
> int interrupt_line_quirk;
>
> static void __devinit quirk_via_bridge(struct pci_dev *pdev)
> {
>         if(pdev->devfn == 0)
>                 interrupt_line_quirk = 1;
> }
>
> The i386 pirq_enable_irq honors this:
>         /* VIA bridges use interrupt line for apic/pci steering across
>            the V-Link */
>         else if (interrupt_line_quirk)
>                 pci_write_config_byte(dev, PCI_INTERRUPT_LINE, dev->irq);
>
> The matching function in ACPI does not honor this quirk, so we probably
> have routing troubles on a lot of affected VIA northbridges.  There's
> at least one thing which looks like an example of this in Bugzilla
> (which was "fixed" by twiddling the IRQ balancing code).  With this
> patch I get a little better (more predictable, at least) behavior.


You're certainly on the right track.  Len and I have discussed how to 
best handle this in ACPI, I'll let him comment further...

	Jeff



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