drm/i915/gen8: Add WaDisableCtxRestoreArbitration workaround

In Indirect and Per context w/a batch buffer,
+WaDisableCtxRestoreArbitration

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Gordon <david.s.gordon@intel.com>
Signed-off-by: Rafael Barbalho <rafael.barbalho@intel.com>
Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_lrc.c

@@ -1140,8 +1140,8 @@ static int gen8_init_indirectctx_bb(struct intel_engine_cs *ring,
 {
 	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
 
-	/* FIXME: Replace me with WA */
-	wa_ctx_emit(batch, MI_NOOP);
+	/* WaDisableCtxRestoreArbitration:bdw,chv */
+	wa_ctx_emit(batch, MI_ARB_ON_OFF | MI_ARB_DISABLE);
 
 	/* Pad to end of cacheline */
 	while (index % CACHELINE_DWORDS)
@@ -1179,6 +1179,9 @@ static int gen8_init_perctx_bb(struct intel_engine_cs *ring,
 {
 	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
 
+	/* WaDisableCtxRestoreArbitration:bdw,chv */
+	wa_ctx_emit(batch, MI_ARB_ON_OFF | MI_ARB_ENABLE);
+
 	wa_ctx_emit(batch, MI_BATCH_BUFFER_END);
 
 	return wa_ctx_end(wa_ctx, *offset = index, 1);