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)); + if (!USES_PPGTT(dev_priv->dev)) + /* 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); + else + 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)); /* XXX: spec defines this as 2 distinct registers. It's unclear if a 64b * write would work. */ -- 1.9.3 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
