1 files changed, 24 insertions, 1 deletions

diff --git a/drivers/char/agp/intel-agp.c b/drivers/char/agp/intel-agp.c
index a3e10dc7cc25..f499c5e0ca54 100644
--- a/drivers/char/agp/intel-agp.c
+++ b/drivers/char/agp/intel-agp.c
@@ -175,6 +175,10 @@ extern int agp_memory_reserved;
 #define SNB_GMCH_GMS_STOLEN_448M        (0xe << 3)
 #define SNB_GMCH_GMS_STOLEN_480M        (0xf << 3)
 #define SNB_GMCH_GMS_STOLEN_512M        (0x10 << 3)
+#define SNB_GTT_SIZE_0M                 (0 << 8)
+#define SNB_GTT_SIZE_1M                 (1 << 8)
+#define SNB_GTT_SIZE_2M                 (2 << 8)
+#define SNB_GTT_SIZE_MASK               (3 << 8)
 
 static const struct aper_size_info_fixed intel_i810_sizes[] =
 {
@@ -1438,6 +1442,8 @@ static unsigned long intel_i965_mask_memory(struct agp_bridge_data *bridge,
 
 static void intel_i965_get_gtt_range(int *gtt_offset, int *gtt_size)
 {
+        u16 snb_gmch_ctl;
+
         switch (agp_bridge->dev->device) {
         case PCI_DEVICE_ID_INTEL_GM45_HB:
         case PCI_DEVICE_ID_INTEL_EAGLELAKE_HB:
@@ -1449,9 +1455,26 @@ static void intel_i965_get_gtt_range(int *gtt_offset, int *gtt_size)
         case PCI_DEVICE_ID_INTEL_IRONLAKE_M_HB:
         case PCI_DEVICE_ID_INTEL_IRONLAKE_MA_HB:
         case PCI_DEVICE_ID_INTEL_IRONLAKE_MC2_HB:
+                *gtt_offset = *gtt_size = MB(2);
+                break;
         case PCI_DEVICE_ID_INTEL_SANDYBRIDGE_HB:
         case PCI_DEVICE_ID_INTEL_SANDYBRIDGE_M_HB:
-                *gtt_offset = *gtt_size = MB(2);
+                *gtt_offset = MB(2);
+
+                pci_read_config_word(intel_private.pcidev, SNB_GMCH_CTRL, &snb_gmch_ctl);
+                switch (snb_gmch_ctl & SNB_GTT_SIZE_MASK) {
+                default:
+                case SNB_GTT_SIZE_0M:
+                        printk(KERN_ERR "Bad GTT size mask: 0x%04x.\n", snb_gmch_ctl);
+                        *gtt_size = MB(0);
+                        break;
+                case SNB_GTT_SIZE_1M:
+                        *gtt_size = MB(1);
+                        break;
+                case SNB_GTT_SIZE_2M:
+                        *gtt_size = MB(2);
+                        break;
+                }
                 break;
         default:
                 *gtt_offset = *gtt_size = KB(512);