drm/i915: Stop touching hangcheck.seqno from intel_engine_init_global_seqno()

The hangcheck runs independently to the main flow of seqno through the
driver. However, we have an odd coupling of the seqno reset that is
unwelcome, and if poked at just the right rate can cause spurious hangs
(e.g. gem_exec_whisper) on an apparently idle engine.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421083113.21321-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -265,6 +265,7 @@ void intel_engine_init_global_seqno(struct intel_engine_cs *engine, u32 seqno)
 	struct drm_i915_private *dev_priv = engine->i915;
 
 	GEM_BUG_ON(!intel_engine_is_idle(engine));
+	GEM_BUG_ON(i915_gem_active_isset(&engine->timeline->last_request));
 
 	/* Our semaphore implementation is strictly monotonic (i.e. we proceed
 	 * so long as the semaphore value in the register/page is greater
@@ -296,9 +297,6 @@ void intel_engine_init_global_seqno(struct intel_engine_cs *engine, u32 seqno)
 	intel_write_status_page(engine, I915_GEM_HWS_INDEX, seqno);
 	clear_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted);
 
-	GEM_BUG_ON(i915_gem_active_isset(&engine->timeline->last_request));
-	engine->hangcheck.seqno = seqno;
-
 	/* After manually advancing the seqno, fake the interrupt in case
 	 * there are any waiters for that seqno.
 	 */