Re: dmesg: PCI interrupts are no longer routed automatically.........

From: linux-os (linux-os_at_chaos.analogic.com)
Date: 01/05/05

  • Next message: Jack O'Quin: "Re: [PATCH] [request for inclusion] Realtime LSM" 
    Date:	Wed, 5 Jan 2005 13:15:30 -0500 (EST)
To: Bjorn Helgaas <bjorn.helgaas@hp.com>

    On Wed, 5 Jan 2005, Bjorn Helgaas wrote:

    > On Wed, 2005-01-05 at 07:06 -0500, linux-os wrote:
    >> The temporary work-around is....
    >> pci_enable_device(pdev);
    >> save_irq = pdev->irq;
    >> pci_disable_device(pdev); // Turn back off.
    >>
    >> init_bars(....);
    >> request_irq(save_irq,...) // Put ISR in place
    >>
    >> pci_write_config_byte(pdev, PCI_CACHE_LINE_SIZE, 0x08);
    >> pci_write_config_byte(pdev, PCI_LATENCY_TIMER, 0x40);
    >> pci_set_dma_mask(pdev, 0x00000000ffffffffULL);
    >> pci_set_drvdata(pdev, NULL);
    >> pci_set_power_state(pdev, 0);
    >> pci_set_master(pdev);
    >> pci_set_mwi(pdev);
    >> pci_write_config_dword(pdev, PCI_COMMAND, PCI_CONFIG);
    >>
    >> .... configure chip-specific stuff, clear interrupts, etc.
    >> pci_enable_device(dev);
    >
    > So prior to 2.6.10, you did something like this?
    >
    > request_irq(pdev->irq, ...);
    > pci_write_config_byte(pdev, PCI_CACHE_LINE_SIZE, 0x08);
    > pci_write_config_byte(pdev, PCI_LATENCY_TIMER, 0x40);
    > ...
    > pci_enable_device(pdev);
    >

    Yes, exactly.

    > What sort of interrupts does the device generate before it's
    > enabled? I can't find anything in the PCI spec that actually
    > prohibits interrupts before the driver starts up the device,
    > but it does seem strange.
    >

    The problem is that the PLX-9656BA INTCSR is not in configuration
    space, but runtime registers off a BAR. The interrupt source
    can be from a PLD that hasn't even had its microcode loaded
    yet!

    FYI, the PLX or similar clone is the bus interface chip for many
    busmastering PCI boards.

    > You wouldn't want your ISR mucking around with a half-initialized
    > device, so does it have to check a "device_configured" flag
    > or something?
    >

    Yes. If the device isn't configured, the ISR reads all the INTCSR
    bits, then writes 0 to the register to prevent anything else.

    If the PLX had been reset, then the INTCSR bits would all
    be masked off. However, reset is really only guaranteed from
    power OFF on some motherboards, in particuar the ones with
    so-called "hot-swap" capabilites fail. There is a software
    reset that, in fact, even reloads its serial EEPROM. However,
    the BAR needs to be accessible for this to be used.

    So it would be wonderful if the correct IRQ could be made
    available before the chip could generate an interrupt.

    Cheers,
    Dick Johnson
    Penguin : Linux version 2.6.10 on an i686 machine (5537.79 BogoMips).
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  • Next message: Jack O'Quin: "Re: [PATCH] [request for inclusion] Realtime LSM"

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