drm/i915: disable interrupts earlier in the driver unload code

Our rps code relies on the interrupts being off to prevent re-arming
of the work items at inopportune moments.

Also drop the redundant cancel_work for the main rps work,
disable_gt_powersave already takes care of that.

Finally add a WARN_ON to ensure we obey that piece of ordering
constraint. Long term I want to lock down the setup/teardown code in a
similar way to how we painstakingly check modeset sequence constraints
already.

v2: Disable polling after hpd handling is shut down - since Egbert's
hpd irq storm handling the hotplug work can re-arm the polling
handler. Spotted by Jani Nikula.

Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -9530,12 +9530,23 @@ void intel_modeset_cleanup(struct drm_device *dev)
 	struct drm_crtc *crtc;
 	struct intel_crtc *intel_crtc;
 
+	/*
+	 * Interrupts and polling as the first thing to avoid creating havoc.
+	 * Too much stuff here (turning of rps, connectors, ...) would
+	 * experience fancy races otherwise.
+	 */
+	drm_irq_uninstall(dev);
+	cancel_work_sync(&dev_priv->hotplug_work);
+	/*
+	 * Due to the hpd irq storm handling the hotplug work can re-arm the
+	 * poll handlers. Hence disable polling after hpd handling is shut down.
+	 */
 	drm_kms_helper_poll_fini(dev);
+
 	mutex_lock(&dev->struct_mutex);
 
 	intel_unregister_dsm_handler();
 
-
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
 		/* Skip inactive CRTCs */
 		if (!crtc->fb)
@@ -9553,12 +9564,6 @@ void intel_modeset_cleanup(struct drm_device *dev)
 
 	mutex_unlock(&dev->struct_mutex);
 
-	/* Disable the irq before mode object teardown, for the irq might
-	 * enqueue unpin/hotplug work. */
-	drm_irq_uninstall(dev);
-	cancel_work_sync(&dev_priv->hotplug_work);
-	cancel_work_sync(&dev_priv->rps.work);
-
 	/* flush any delayed tasks or pending work */
 	flush_scheduled_work();
 

drivers/gpu/drm/i915/intel_pm.c

@@ -3671,6 +3671,9 @@ void intel_disable_gt_powersave(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	/* Interrupts should be disabled already to avoid re-arming. */
+	WARN_ON(dev->irq_enabled);
+
 	if (IS_IRONLAKE_M(dev)) {
 		ironlake_disable_drps(dev);
 		ironlake_disable_rc6(dev);