drm/i915: Move idle checks before intel_engine_init_global_seqno()

intel_engine_init_globa_seqno() may be called from an uncontrolled
set-wedged path where we have given up waiting for broken hw and declare
it defunct. Along that path, any sanity checks that the hw is idle
before we adjust its state will expectedly fail, so we simply cannot.
Instead of asserting inside init_global_seqno, we move them to the
normal caller reset_all_global_seqno() as it handles runtime seqno
wraparound.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170721123238.16428-8-chris@chris-wilson.co.uk
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_request.c

@@ -213,6 +213,10 @@ static int reset_all_global_seqno(struct drm_i915_private *i915, u32 seqno)
 				cond_resched();
 		}
 
+		/* Check we are idle before we fiddle with hw state! */
+		GEM_BUG_ON(!intel_engine_is_idle(engine));
+		GEM_BUG_ON(i915_gem_active_isset(&engine->timeline->last_request));
+
 		/* Finally reset hw state */
 		intel_engine_init_global_seqno(engine, seqno);
 		tl->seqno = seqno;

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -337,9 +337,6 @@ 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
 	 * than the sync value), so whenever we reset the seqno,