[Intel-gfx] [PATCH] drm/i915: Flush WC GGTT only on required platforms

[Nirmoy Das]

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.vivi at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Jonathan Cavitt <jonathan.cavitt at intel.com>
Cc: John Harrison <john.c.harrison at intel.com>
Cc: Andi Shyti <andi.shyti at linux.intel.com>
Cc: <stable at vger.kernel.org> # v6.2+
Suggested-by: Matt Roper <matthew.d.roper at intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das at 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