drm/i915/guc: Cancel GuC engine busyness worker synchronously

The worker is canceled in gt_park path, but earlier it was assumed that
gt_park path cannot sleep and the cancel is asynchronous. This caused a
race with suspend flow where the worker runs after suspend and causes an
unclaimed register access warning. Cancel the worker synchronously since
the gt_park is indeed allowed to sleep.

v2: Fix author name and sign-off mismatch

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4419
Fixes: 77cdd05 ("drm/i915/pmu: Connect engine busyness stats from GuC to pmu")
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220827002135.139349-1-umesh.nerlige.ramappa@intel.com
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
(cherry picked from commit 31335aa)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

@@ -1438,7 +1438,12 @@ void intel_guc_busyness_park(struct intel_gt *gt)
 	if (!guc_submission_initialized(guc))
 		return;
 
-	cancel_delayed_work(&guc->timestamp.work);
+	/*
+	 * There is a race with suspend flow where the worker runs after suspend
+	 * and causes an unclaimed register access warning. Cancel the worker
+	 * synchronously here.
+	 */
+	cancel_delayed_work_sync(&guc->timestamp.work);
 
 	/*
 	 * Before parking, we should sample engine busyness stats if we need to.