gen8_ggtt_invalidate() is only needed for limitted set of platforms
where GGTT is mapped as WC otherwise this can cause unwanted
side-effects on XE_HP platforms where GFX_FLSH_CNTL_GEN6 is not
valid.

Fixes: d2eae8e98d59 ("drm/i915/dg2: Drop force_probe requirement")
Cc: Rodrigo Vivi <rodrigo.v...@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursu...@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
Cc: Jani Nikula <jani.nik...@linux.intel.com>
Cc: Jonathan Cavitt <jonathan.cav...@intel.com>
Cc: John Harrison <john.c.harri...@intel.com>
Cc: Andi Shyti <andi.sh...@linux.intel.com>
Cc: <sta...@vger.kernel.org> # v6.2+
Suggested-by: Matt Roper <matthew.d.ro...@intel.com>
Signed-off-by: Nirmoy Das <nirmoy....@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_ggtt.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_ggtt.c 
b/drivers/gpu/drm/i915/gt/intel_ggtt.c
index 4d7d88b92632..c2858d434bce 100644
--- a/drivers/gpu/drm/i915/gt/intel_ggtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_ggtt.c
@@ -197,13 +197,17 @@ void gen6_ggtt_invalidate(struct i915_ggtt *ggtt)
 
 static void gen8_ggtt_invalidate(struct i915_ggtt *ggtt)
 {
+       struct drm_i915_private *i915 = ggtt->vm.i915;
        struct intel_uncore *uncore = ggtt->vm.gt->uncore;
 
        /*
         * Note that as an uncached mmio write, this will flush the
         * WCB of the writes into the GGTT before it triggers the invalidate.
+        *
+        * Only perform this when GGTT is mapped as WC, see ggtt_probe_common().
         */
-       intel_uncore_write_fw(uncore, GFX_FLSH_CNTL_GEN6, GFX_FLSH_CNTL_EN);
+       if (!IS_GEN9_LP(i915) && GRAPHICS_VER(i915) < 11)
+               intel_uncore_write_fw(uncore, GFX_FLSH_CNTL_GEN6, 
GFX_FLSH_CNTL_EN);
 }
 
 static void guc_ggtt_invalidate(struct i915_ggtt *ggtt)
-- 
2.41.0

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