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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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