Thanks Carlo to report this problem. The following patch should fix
his and potential issue.

[AGPGART] intel_agp: don't load if no IGD detected and no AGP port

After i915 chip, GMCH has no AGP port. Origin bridge driver in device
table will try to access illegal regs like APBASE, APSIZE, etc. This
may cause problem.

So mark them as NULL in the table, we won't load if no IGD got detect
and bridge has no AGP port.

Signed-off-by: Wang Zhenyu <zhenyu.z.wang@intel.com>
---
 drivers/char/agp/intel-agp.c |   35 +++++++++++++++++++----------------
 1 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/drivers/char/agp/intel-agp.c b/drivers/char/agp/intel-agp.c
index 0439ee9..a124060 100644
--- a/drivers/char/agp/intel-agp.c
+++ b/drivers/char/agp/intel-agp.c
@@ -1843,35 +1843,35 @@ static const struct intel_driver_description {
 		&intel_845_driver, &intel_830_driver },
 	{ PCI_DEVICE_ID_INTEL_82875_HB, 0, 0, "i875", &intel_845_driver, NULL },
 	{ PCI_DEVICE_ID_INTEL_82915G_HB, PCI_DEVICE_ID_INTEL_82915G_IG, 0, "915G",
-		&intel_845_driver, &intel_915_driver },
+		NULL, &intel_915_driver },
 	{ PCI_DEVICE_ID_INTEL_82915GM_HB, PCI_DEVICE_ID_INTEL_82915GM_IG, 0, "915GM",
-		&intel_845_driver, &intel_915_driver },
+		NULL, &intel_915_driver },
 	{ PCI_DEVICE_ID_INTEL_82945G_HB, PCI_DEVICE_ID_INTEL_82945G_IG, 0, "945G",
-		&intel_845_driver, &intel_915_driver },
+		NULL, &intel_915_driver },
 	{ PCI_DEVICE_ID_INTEL_82945GM_HB, PCI_DEVICE_ID_INTEL_82945GM_IG, 1, "945GM",
-		&intel_845_driver, &intel_915_driver },
+		NULL, &intel_915_driver },
 	{ PCI_DEVICE_ID_INTEL_82945GM_HB, PCI_DEVICE_ID_INTEL_82945GME_IG, 0, "945GME",
-		&intel_845_driver, &intel_915_driver },
+		NULL, &intel_915_driver },
 	{ PCI_DEVICE_ID_INTEL_82946GZ_HB, PCI_DEVICE_ID_INTEL_82946GZ_IG, 0, "946GZ",
-		&intel_845_driver, &intel_i965_driver },
+		NULL, &intel_i965_driver },
 	{ PCI_DEVICE_ID_INTEL_82965G_1_HB, PCI_DEVICE_ID_INTEL_82965G_1_IG, 0, "965G",
-		&intel_845_driver, &intel_i965_driver },
+		NULL, &intel_i965_driver },
 	{ PCI_DEVICE_ID_INTEL_82965Q_HB, PCI_DEVICE_ID_INTEL_82965Q_IG, 0, "965Q",
-		&intel_845_driver, &intel_i965_driver },
+		NULL, &intel_i965_driver },
 	{ PCI_DEVICE_ID_INTEL_82965G_HB, PCI_DEVICE_ID_INTEL_82965G_IG, 0, "965G",
-		&intel_845_driver, &intel_i965_driver },
+		NULL, &intel_i965_driver },
 	{ PCI_DEVICE_ID_INTEL_82965GM_HB, PCI_DEVICE_ID_INTEL_82965GM_IG, 1, "965GM",
-		&intel_845_driver, &intel_i965_driver },
+		NULL, &intel_i965_driver },
 	{ PCI_DEVICE_ID_INTEL_82965GM_HB, PCI_DEVICE_ID_INTEL_82965GME_IG, 0, "965GME/GLE",
-		&intel_845_driver, &intel_i965_driver },
+		NULL, &intel_i965_driver },
 	{ PCI_DEVICE_ID_INTEL_7505_0, 0, 0, "E7505", &intel_7505_driver, NULL },
 	{ PCI_DEVICE_ID_INTEL_7205_0, 0, 0, "E7205", &intel_7505_driver, NULL },
 	{ PCI_DEVICE_ID_INTEL_G33_HB, PCI_DEVICE_ID_INTEL_G33_IG, 0, "G33",
-		&intel_845_driver, &intel_g33_driver },
+		NULL, &intel_g33_driver },
 	{ PCI_DEVICE_ID_INTEL_Q35_HB, PCI_DEVICE_ID_INTEL_Q35_IG, 0, "Q35",
-		&intel_845_driver, &intel_g33_driver },
+		NULL, &intel_g33_driver },
 	{ PCI_DEVICE_ID_INTEL_Q33_HB, PCI_DEVICE_ID_INTEL_Q33_IG, 0, "Q33",
-		&intel_845_driver, &intel_g33_driver },
+		NULL, &intel_g33_driver },
 	{ 0, 0, 0, NULL, NULL, NULL }
 };
 
@@ -1917,8 +1917,11 @@ static int __devinit agp_intel_probe(struct pci_dev *pdev,
 	}
 
 	if (bridge->driver == NULL) {
-		printk(KERN_WARNING PFX "Failed to find bridge device "
-			"(chip_id: %04x)\n", intel_agp_chipsets[i].gmch_chip_id);
+		/* bridge has no AGP and no IGD detected */
+		if (cap_ptr)
+			printk(KERN_WARNING PFX "Failed to find bridge device "
+				"(chip_id: %04x)\n",
+				intel_agp_chipsets[i].gmch_chip_id);
 		agp_put_bridge(bridge);
 		return -ENODEV;
         }
-- 
1.4.4.4
-
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