drm/i915: Disable the "binder"

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()

Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Tested-by: Paz Zcharya <pazz@chromium.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240202224340.30647-6-ville.syrjala@linux.intel.com

diff --git a/drivers/gpu/drm/i915/gt/intel_gtt.c b/drivers/gpu/drm/i915/gt/intel_gtt.c
index 86f73fe558ca6eb88051c8e77938460bbc043dec..7811a8c9da0672e4853b3ddfa44123cb5727f4fd 100644 (file)
--- 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)