agp/intel: Use the correct mask to detect i830 aperture size.

BugLink: https://bugs.launchpad.net/bugs/597075

commit f1befe71fa7a79ab733011b045639d8d809924ad introduced a
regression when detecting aperture size of some i915 adapters, e.g.,
those on the Intel Q35 chipset.

The original report: https://bugzilla.kernel.org/show_bug.cgi?id=15733
The regression report: https://bugzilla.kernel.org/show_bug.cgi?id=16294

According to the specification found at
http://intellinuxgraphics.org/VOL_1_graphics_core.pdf, the PCI config
space register I830_GMCH_CTRL is a mirror of GMCH Graphics
Control. The correct macro for isolating the aperture size bits is
therefore I830_GMCH_GMS_MASK along with the attendant changes to the
case statement.

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Tested-by: Kees Cook <kees.cook@canonical.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Eric Anholt <eric@anholt.net>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 8 insertions, 5 deletions

diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
index 9344216183a4..a7547150a705 100644
--- a/drivers/char/agp/intel-gtt.c
+++ b/drivers/char/agp/intel-gtt.c
@@ -1216,17 +1216,20 @@ static int intel_i915_get_gtt_size(void)
 
                 /* G33's GTT size defined in gmch_ctrl */
                 pci_read_config_word(agp_bridge->dev, I830_GMCH_CTRL, &gmch_ctrl);
-                switch (gmch_ctrl & G33_PGETBL_SIZE_MASK) {
-                case G33_PGETBL_SIZE_1M:
+                switch (gmch_ctrl & I830_GMCH_GMS_MASK) {
+                case I830_GMCH_GMS_STOLEN_512:
+                        size = 512;
+                        break;
+                case I830_GMCH_GMS_STOLEN_1024:
                         size = 1024;
                         break;
-                case G33_PGETBL_SIZE_2M:
-                        size = 2048;
+                case I830_GMCH_GMS_STOLEN_8192:
+                        size = 8*1024;
                         break;
                 default:
                         dev_info(&agp_bridge->dev->dev,
                                  "unknown page table size 0x%x, assuming 512KB\n",
-                                (gmch_ctrl & G33_PGETBL_SIZE_MASK));
+                                (gmch_ctrl & I830_GMCH_GMS_MASK));
                         size = 512;
                 }
         } else {