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drm/i915: Don't do MTRR setup if PAT is enabled 

Some newer BIOSes are shipping with all MTRRs already populated.  These
BIOSes are all on machines with sufficiently new CPUs that the
referenced errata doesn't apply anyway, so just don't try to claim the
MTRR.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41648
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Adam Jackson 2012-03-14 11:22:11 -04:00 committed by Daniel Vetter
parent e2b665c480
commit 9e984bc1df
1 changed files with 6 additions and 0 deletions
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6
drivers/gpu/drm/i915/i915_dma.c
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@ -43,6 +43,7 @@
#include <linux/slab.h>
#include <linux/module.h>
#include <acpi/video.h>
#include <asm/pat.h>
static void i915_write_hws_pga(struct drm_device *dev)
{
@ -1918,6 +1919,11 @@ static void
i915_mtrr_setup(struct drm_i915_private *dev_priv, unsigned long base,
unsigned long size)
{
#if defined(CONFIG_X86_PAT)
if (cpu_has_pat)
return;
#endif
/* Set up a WC MTRR for non-PAT systems. This is more common than
* one would think, because the kernel disables PAT on first
* generation Core chips because WC PAT gets overridden by a UC