agp/intel: Don't do the chipset flush on Sandybridge.

This CPU should be coherent with graphics in this direction, though
flushing graphics caches are still required.  Fixes a system reset on
module load on Sandybridge with 4G+ memory.
Signed-off-by: NEric Anholt <eric@anholt.net>

drivers/char/agp/intel-agp.c

@@ -97,6 +97,9 @@ EXPORT_SYMBOL(intel_agp_enabled);
 #define IS_PINEVIEW (agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_PINEVIEW_M_HB || \
 		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_PINEVIEW_HB)
 
+#define IS_SNB (agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_SANDYBRIDGE_HB || \
+		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_SANDYBRIDGE_M_HB)
+
 #define IS_G4X (agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_EAGLELAKE_HB || \
 		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_Q45_HB || \
 		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_G45_HB || \
@@ -107,8 +110,7 @@ EXPORT_SYMBOL(intel_agp_enabled);
 		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_IRONLAKE_M_HB || \
 		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_IRONLAKE_MA_HB || \
 		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_IRONLAKE_MC2_HB || \
-		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_SANDYBRIDGE_HB || \
-		agp_bridge->dev->device == PCI_DEVICE_ID_INTEL_SANDYBRIDGE_M_HB)
+		IS_SNB)
 
 extern int agp_memory_reserved;
 
@@ -1204,6 +1206,9 @@ static void intel_i9xx_setup_flush(void)
 	if (intel_private.ifp_resource.start)
 		return;
 
+	if (IS_SNB)
+		return;
+
 	/* setup a resource for this object */
 	intel_private.ifp_resource.name = "Intel Flush Page";
 	intel_private.ifp_resource.flags = IORESOURCE_MEM;