On Thu, Oct 30, 2014 at 09:18:18AM -0700, Rodrigo Vivi wrote: > Global GTT doesn't have pat_sel[2:0] so it always point to pat_sel = 000; > So the only way to avoid screen corruptions is setting PAT 0 to Uncached. > > MOCS can still be used though. But if userspace is trusting PTE for > cache selection the safest thing to do is to let caches disabled. > > BSpec: "For GGTT, there is NO pat_sel[2:0] from the entry, > so RTL will always use the value corresponding to pat_sel = 000" > > Reference: https://bugs.freedesktop.org/show_bug.cgi?id=85576 > Cc: James Ausmus <james.aus...@intel.com> > Signed-off-by: Rodrigo Vivi <rodrigo.v...@intel.com> > --- > drivers/gpu/drm/i915/i915_gem_gtt.c | 29 +++++++++++++++++++++-------- > 1 file changed, 21 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c > b/drivers/gpu/drm/i915/i915_gem_gtt.c > index cb7adab..24b4f27 100644 > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c > @@ -1911,14 +1911,27 @@ static void bdw_setup_private_ppat(struct > drm_i915_private *dev_priv) > { > uint64_t pat; > > - pat = GEN8_PPAT(0, GEN8_PPAT_WB | GEN8_PPAT_LLC) | /* for normal > objects, no eLLC */ > - GEN8_PPAT(1, GEN8_PPAT_WC | GEN8_PPAT_LLCELLC) | /* for something > pointing to ptes? */ > - GEN8_PPAT(2, GEN8_PPAT_WT | GEN8_PPAT_LLCELLC) | /* for scanout > with eLLC */ > - GEN8_PPAT(3, GEN8_PPAT_UC) | /* Uncached > objects, mostly for scanout */ > - GEN8_PPAT(4, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(0)) > | > - GEN8_PPAT(5, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(1)) > | > - GEN8_PPAT(6, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(2)) > | > - GEN8_PPAT(7, GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(3));
Instead of deleting this and making a rather ugly if, Just > + if (!USES_PPGTT(dev_priv)) > + /* Spec: "For GGTT, there is NO pat_sel[2:0] from the entry, > + * so RTL will always use the value corresponding to > + * pat_sel = 000". > + * So let's disable cache for GGTT to avoid screen corruptions. > + * MOCS still can be used though. > + */ > + pat = GEN8_PPAT(0, GEN8_PPAT_UC); to override in the unlikely case of disabling ppgtt. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
