[PATCH v4 05/16] drm/i915: Disable the "binder"

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Now that the GGTT PTE updates go straight to GSMBASE (bypassing
GTTMMADR) there should be no more risk of system hangs? So the
"binder" (ie. update the PTEs via MI_UPDATE_GTT) is no longer
necessary, disable it.

My main worry with the MI_UPDATE_GTT are:
- only used on this one platform so very limited testing coverage
- async so more opprtunities to screw things up
- what happens if the engine hangs while we're waiting for MI_UPDATE_GTT
  to finish?
- requires working command submission, so even getting a working
  display now depends on a lot more extra components working correctly

TODO: MI_UPDATE_GTT might be interesting as an optimization
though, so perhaps someone should look into always using it
(assuming the GPU is alive and well)?

v2: Keep using MI_UPDATE_GTT on VM guests
v3: use i915_direct_stolen_access()

Cc: Paz Zcharya <pazz at chromium.org>
Cc: Nirmoy Das <nirmoy.das at intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_gtt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c b/drivers/gpu/drm/i915/gt/intel_gtt.c
index 86f73fe558ca..7811a8c9da06 100644
--- a/drivers/gpu/drm/i915/gt/intel_gtt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gtt.c
@@ -24,7 +24,8 @@
 bool i915_ggtt_require_binder(struct drm_i915_private *i915)
 {
 	/* Wa_13010847436 & Wa_14019519902 */
-	return MEDIA_VER_FULL(i915) == IP_VER(13, 0);
+	return !i915_direct_stolen_access(i915) &&
+		MEDIA_VER_FULL(i915) == IP_VER(13, 0);
 }
 
 static bool intel_ggtt_update_needs_vtd_wa(struct drm_i915_private *i915)
-- 
2.43.0