By default i915_ttm_cache_level() decides I915_CACHE_LLC if HAS_SNOOP.
This is divergent from existing backends code which only considers
HAS_LLC.
Testing shows that trusting snooping on gen5- is unreliable and bsw via
ggtt mappings, so limit DGFX for now and maintain previous behaviour.

Signed-off-by: Robert Beckett <bob.beck...@collabora.com>
Reviewed-by: Thomas Hellström <thomas.hellst...@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c 
b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
index 4c1de0b4a10f..40249fa28a7a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
@@ -46,7 +46,9 @@ static enum i915_cache_level
 i915_ttm_cache_level(struct drm_i915_private *i915, struct ttm_resource *res,
                     struct ttm_tt *ttm)
 {
-       return ((HAS_LLC(i915) || HAS_SNOOP(i915)) &&
+       bool can_snoop = HAS_SNOOP(i915) && IS_DGFX(i915);
+
+       return ((HAS_LLC(i915) || can_snoop) &&
                !i915_ttm_gtt_binds_lmem(res) &&
                ttm->caching == ttm_cached) ? I915_CACHE_LLC :
                I915_CACHE_NONE;
-- 
2.25.1

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