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    Subject[PATCH] agp: ensure GART has an address before enabling it
    Some BIOSs (eg. the AMI BIOS on the Asus P4P800 motherboard) don't
    initialise the GART address, and pcibios_assign_resources() can ignore
    it because it can be marked as a host bridge (see
    https://bugzilla.kernel.org/show_bug.cgi?id=24392#c5 for
    details). This was handled correctly up to 2.6.35, but the
    pci_enable_device() cleanup in 2.6.36 means that the kernel tries to
    enable the GART before assigning it an address; in such cases the GART
    overlaps with other device assignments and ends up being disabled.

    This patch fixes #24392.

    Note that I imagine efficeon-agp.c probably has the same problem, but
    I can't test that and I'd like to make sure this patch is suitable for
    -stable (since 2.6.36 and 2.6.37 are affected).

    Cc: <stable@kernel.org>
    Signed-off-by: Stephen Kitt <steve@sk2.org>
    ---
    diff --git a/drivers/char/agp/intel-agp.c b/drivers/char/agp/intel-agp.c
    index 857df10..b0a0dcc 100644
    --- a/drivers/char/agp/intel-agp.c
    +++ b/drivers/char/agp/intel-agp.c
    @@ -774,20 +774,14 @@ static int __devinit agp_intel_probe(struct pci_dev *pdev,
    dev_info(&pdev->dev, "Intel %s Chipset\n", intel_agp_chipsets[i].name);

    /*
    - * If the device has not been properly setup, the following will catch
    - * the problem and should stop the system from crashing.
    - * 20030610 - hamish@zot.org
    - */
    - if (pci_enable_device(pdev)) {
    - dev_err(&pdev->dev, "can't enable PCI device\n");
    - agp_put_bridge(bridge);
    - return -ENODEV;
    - }
    -
    - /*
    * The following fixes the case where the BIOS has "forgotten" to
    * provide an address range for the GART.
    * 20030610 - hamish@zot.org
    + * This happens before pci_enable_device() intentionally;
    + * calling pci_enable_device() before assigning the resource
    + * will result in the GART being disabled on machines with such
    + * BIOSs (the GART ends up with a BAR starting at 0, which
    + * conflicts a lot of other devices).
    */
    r = &pdev->resource[0];
    if (!r->start && r->end) {
    @@ -798,6 +792,17 @@ static int __devinit agp_intel_probe(struct pci_dev *pdev,
    }
    }

    + /*
    + * If the device has not been properly setup, the following will catch
    + * the problem and should stop the system from crashing.
    + * 20030610 - hamish@zot.org
    + */
    + if (pci_enable_device(pdev)) {
    + dev_err(&pdev->dev, "can't enable PCI device\n");
    + agp_put_bridge(bridge);
    + return -ENODEV;
    + }
    +
    /* Fill in the mode register */
    if (cap_ptr) {
    pci_read_config_dword(pdev,

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