drm/i915: Cancel hangcheck before GPU is suspended

In order to avoid accessing GPU registers while GPU is suspended cancel
the hangcheck work before calling intel_suspend_complete which actually
puts the GPU to suspend. Otherwise hangcheck might do MMIO reads to a
suspended GPU.

Placement before intel_guc_suspend is imitated from i915_drm_suspend
which cancels the work at i915_gem_suspend, to keep the functions
similar.

On VLV systems, namely BYT, this was causing an error during runtime
suspend cycle:

[drm:vlv_check_no_gt_access [i915]] *ERROR* GT register access while GT waking disabled

Testcase: igt/pm_rpm/basic-rte
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93121Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1449669373-8588-1-git-send-email-joonas.lahtinen@linux.intel.comReviewed-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Imre Deak <imre.deak@intel.com>

drivers/gpu/drm/i915/i915_drv.c

@@ -1462,6 +1462,8 @@ static int intel_runtime_suspend(struct device *device)
 	i915_gem_release_all_mmaps(dev_priv);
 	mutex_unlock(&dev->struct_mutex);
 
+	cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);
+
 	intel_guc_suspend(dev);
 
 	intel_suspend_gt_powersave(dev);
@@ -1475,7 +1477,6 @@ static int intel_runtime_suspend(struct device *device)
 		return ret;
 	}
 
-	cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);
 	intel_uncore_forcewake_reset(dev, false);
 	dev_priv->pm.suspended = true;