Re: 2.6.8-rc4-mm1 doesn't boot

From: Len Brown (len.brown_at_intel.com)
Date: 08/13/04

  • Next message: Len Brown: "Re: Allow userspace do something special on overtemp" 
    To: Bjorn Helgaas <bjorn.helgaas@hp.com>
Date:	12 Aug 2004 18:43:00 -0400

    On Thu, 2004-08-12 at 17:50, Bjorn Helgaas wrote:
    > On Wednesday 11 August 2004 3:32 pm, Len Brown wrote:
    > > I've never understood this floppy IRQ6 business.
    > > Apparently it requests IRQ6, but doesn't show up in /proc/interrupts
    >
    > floppy_init() requests IRQ6, but then frees it before returning. It
    > looks like the driver only holds onto it while the device is actually
    > open, which explains why it doesn't usually show up in
    > /proc/interrupts.

    ah, the mysterious floppy.c -- explained;-)

    > Len later wrote:
    > > I assert it is a BIOS bug for the BIOS to set LNKD to
    > > IRQ6 if there is a floppy present and enabled; but fair
    > > game if there is no floppy. Though perhaps floppy.c
    > > doesn't understand that.
    >
    > Adrian has the floppies disabled in the BIOS, so maybe it's
    > legit to use IRQ6 for the NIC PCI interrupt. But floppy.c
    > doesn't check for anything like that as far as I can see.
    >
    > The fact that floppy.c seems to be able to poke the controller
    > and get an interrupt back (with "pci=routeirq") suggests to me
    > that the floppy controller responds even when disabled in the
    > BIOS, and that it actually expects IRQ6 to be level-triggered,
    > but the BIOS is leaving it configured as edge-triggered.

    I expect that the the bug is that floppy.c, like other motherboard
    devices, should take advantage of ACPI for device resource
    enumeration. This is one of the gaps I described at OLS,
    and it is embodied in this bug report:
    http://bugzilla.kernel.org/show_bug.cgi?id=2733

    My expectation is that if the SETUP option is changed to
    enable the floppy (the controller is probably burried inside
    an LPC super-io or south bridge, even if there is no physical
    drive in the box) Then we should see

    ACPI: PCI Interrupt Link [LNKD] (IRQs 3 4 5 *6 7 10 11 12 14 15)
    turn into

    ACPI: PCI Interrupt Link [LNKD] (IRQs 3 4 5 6 7 10 *11 12 14 15)

    with the * moving off of 6 (11 in this example) showing that
    the BIOS selected a different active IRQ for this link.

    Or even
    ACPI: PCI Interrupt Link [LNKD] (IRQs 3 4 5 7 10 *11 12 14 15)

    Where IRQ6 is not in the possible-list, which would prevent
    Linux from setting the device to that IRQ even if we wanted to.
    (and again, the '*' on some other IRQ, 11 in this example)

    Adrian, if you enable your not-present floppy in the BIOS,
    what does Linux do?

    thanks,
    -Len

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  • Next message: Len Brown: "Re: Allow userspace do something special on overtemp"

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