drm/i915: Reset the breadcrumbs IRQ more carefully

Along with the interrupt, we want to restore the fake-irq and
wait-timeout detection. If we use the breadcrumbs interface to setup the
interrupt as it wants, the auxiliary timers will also be restored.

v2: Cancel both timers as well, sanitize the IMR.

Fixes: 821ed7df6e2a ("drm/i915: Update reset path to fix incomplete requests")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161007065327.24515-3-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index 9bad14d..495611b 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -578,6 +578,36 @@
 	return 0;
 }
 
+static void cancel_fake_irq(struct intel_engine_cs *engine)
+{
+	struct intel_breadcrumbs *b = &engine->breadcrumbs;
+
+	del_timer_sync(&b->hangcheck);
+	del_timer_sync(&b->fake_irq);
+	clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings);
+}
+
+void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine)
+{
+	struct intel_breadcrumbs *b = &engine->breadcrumbs;
+
+	cancel_fake_irq(engine);
+	spin_lock(&b->lock);
+
+	__intel_breadcrumbs_disable_irq(b);
+	if (intel_engine_has_waiter(engine)) {
+		b->timeout = wait_timeout();
+		__intel_breadcrumbs_enable_irq(b);
+		if (READ_ONCE(b->irq_posted))
+			wake_up_process(b->first_wait->tsk);
+	} else {
+		/* sanitize the IMR and unmask any auxiliary interrupts */
+		irq_disable(engine);
+	}
+
+	spin_unlock(&b->lock);
+}
+
 void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
 {
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;
@@ -585,8 +615,7 @@
 	if (!IS_ERR_OR_NULL(b->signaler))
 		kthread_stop(b->signaler);
 
-	del_timer_sync(&b->hangcheck);
-	del_timer_sync(&b->fake_irq);
+	cancel_fake_irq(engine);
 }
 
 unsigned int intel_kick_waiters(struct drm_i915_private *i915)