drm/i915: Use b->irq_enable() as predicate for mock engine

Since commit  d4ccceb0 ("drm/i915/icl: Ringbuffer interrupt handling")
we have required a mechanism to avoid touching the interrupt hardware
for breadcrumbs, superseding our mock interface for selftests.

The residual problem (ideas welcome) is in probing the mock ring
registers for ring_is_idle. Hmm, maybe we should just install
mock handlers for i915->uncore.mmio__write and friends? Only problem
being is that we would to truly mock some expected reads. :(

References: d4ccceb0 ("drm/i915/icl: Ringbuffer interrupt handling")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190118112225.13780-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_breadcrumbs.c

@@ -287,25 +287,16 @@ static bool __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b)
 	if (b->irq_armed)
 		return false;
 
-	/* The breadcrumb irq will be disarmed on the interrupt after the
+	/*
+	 * The breadcrumb irq will be disarmed on the interrupt after the
 	 * waiters are signaled. This gives us a single interrupt window in
 	 * which we can add a new waiter and avoid the cost of re-enabling
 	 * the irq.
 	 */
 	b->irq_armed = true;
 
-	if (I915_SELFTEST_ONLY(b->mock)) {
-		/* For our mock objects we want to avoid interaction
-		 * with the real hardware (which is not set up). So
-		 * we simply pretend we have enabled the powerwell
-		 * and the irq, and leave it up to the mock
-		 * implementation to call intel_engine_wakeup()
-		 * itself when it wants to simulate a user interrupt,
-		 */
-		return true;
-	}
-
-	/* Since we are waiting on a request, the GPU should be busy
+	/*
+	 * Since we are waiting on a request, the GPU should be busy
 	 * and should have its own rpm reference. This is tracked
 	 * by i915->gt.awake, we can forgo holding our own wakref
 	 * for the interrupt as before i915->gt.awake is released (when

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -917,6 +917,9 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
 	intel_wakeref_t wakeref;
 	bool idle = true;
 
+	if (I915_SELFTEST_ONLY(!engine->mmio_base))
+		return true;
+
 	/* If the whole device is asleep, the engine must be idle */
 	wakeref = intel_runtime_pm_get_if_in_use(dev_priv);
 	if (!wakeref)
@@ -955,9 +958,6 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
 	if (!intel_engine_signaled(engine, intel_engine_last_submit(engine)))
 		return false;
 
-	if (I915_SELFTEST_ONLY(engine->breadcrumbs.mock))
-		return true;
-
 	/* Waiting to drain ELSP? */
 	if (READ_ONCE(engine->execlists.active)) {
 		struct tasklet_struct *t = &engine->execlists.tasklet;
@@ -983,10 +983,7 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
 		return false;
 
 	/* Ring stopped? */
-	if (!ring_is_idle(engine))
-		return false;
-
-	return true;
+	return ring_is_idle(engine);
 }
 
 bool intel_engines_are_idle(struct drm_i915_private *dev_priv)

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -398,7 +398,6 @@ struct intel_engine_cs {
 		unsigned int irq_count;
 
 		bool irq_armed : 1;
-		I915_SELFTEST_DECLARE(bool mock : 1);
 	} breadcrumbs;
 
 	struct {

drivers/gpu/drm/i915/selftests/mock_engine.c

@@ -201,7 +201,6 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
 	i915_timeline_set_subclass(&engine->base.timeline, TIMELINE_ENGINE);
 
 	intel_engine_init_breadcrumbs(&engine->base);
-	engine->base.breadcrumbs.mock = true; /* prevent touching HW for irqs */
 
 	/* fake hw queue */
 	spin_lock_init(&engine->hw_lock);