[Intel-gfx] [PATCH 1/2] drm/i915/gt: Ensure 'ENABLE_BOOT_FETCH' is enabled before ppGTT

[Chris Wilson]

Cryptic notes in bspec say that "The MBC Driver Boot Enable bit in MBCTL
register must be set before this register is written to upon boot up
(including S3 exit)."

We tried adding it to our list of verified workarounds, but our
self checks spot that the bit does not stick. It's only meant to be
cleared after a FLR. As it fails our verification, just blindly apply
the bit prior to loading the ppGTT.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_ring_submission.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
index f70b903a98bc..ab58694c3320 100644
--- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
@@ -642,6 +642,9 @@ static void set_pp_dir(struct intel_engine_cs *engine)
 	if (vm) {
 		struct i915_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
 
+		intel_uncore_rmw(engine->uncore, GEN6_MBCTL,
+				 0, GEN6_MBCTL_ENABLE_BOOT_FETCH);
+
 		ENGINE_WRITE(engine, RING_PP_DIR_DCLV, PP_DIR_DCLV_2G);
 		ENGINE_WRITE(engine, RING_PP_DIR_BASE,
 			     px_base(ppgtt->pd)->ggtt_offset << 10);
-- 
2.25.0