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>

diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
index 9344216183a433a84210b5ebaef0efd57e6aa9c7..a7547150a705235f75f7949f89ebd99a8e3ba329 100644 (file)
--- 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 {