drm/i915: Finish the wait-for-wedge by retiring all the inflight requests

Before we reset the GPU after marking the device as wedged, we wait for
all the remaining requests to be completed (and marked as EIO).
Afterwards, we should flush the request lists so the next batch start
with the driver in an idle state.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180307134226.25492-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -3281,7 +3281,8 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
 	if (!test_bit(I915_WEDGED, &i915->gpu_error.flags))
 		return true;
 
-	/* Before unwedging, make sure that all pending operations
+	/*
+	 * Before unwedging, make sure that all pending operations
 	 * are flushed and errored out - we may have requests waiting upon
 	 * third party fences. We marked all inflight requests as EIO, and
 	 * every execbuf since returned EIO, for consistency we want all
@@ -3299,7 +3300,8 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
 			if (!rq)
 				continue;
 
-			/* We can't use our normal waiter as we want to
+			/*
+			 * We can't use our normal waiter as we want to
 			 * avoid recursively trying to handle the current
 			 * reset. The basic dma_fence_default_wait() installs
 			 * a callback for dma_fence_signal(), which is
@@ -3314,8 +3316,11 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
 				return false;
 		}
 	}
+	i915_retire_requests(i915);
+	GEM_BUG_ON(i915->gt.active_requests);
 
-	/* Undo nop_submit_request. We prevent all new i915 requests from
+	/*
+	 * Undo nop_submit_request. We prevent all new i915 requests from
 	 * being queued (by disallowing execbuf whilst wedged) so having
 	 * waited for all active requests above, we know the system is idle
 	 * and do not have to worry about a thread being inside