drm/i915: Supply the engine-id for our mock_engine()

In the original selftest, we didn't care what the engine->id was, just
that it could uniquely identify it. Later though, we started tracking
the mock engines in the fixed size arrays around the drm_i915_private and
so we now require their indices to be correct. This becomes an issue when
using the standalone harness which runs all available tests at module load,
and so we quickly assign an out-of-bounds index to an engine as we
reallocate the mock GEM device between tests. It doesn't show up in
igt/drv_selftest as that runs each subtest individually.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102045
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20170809163930.26470-1-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

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

@@ -123,10 +123,12 @@ static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
 }
 
 struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
-				    const char *name)
+				    const char *name,
+				    int id)
 {
 	struct mock_engine *engine;
-	static int id;
+
+	GEM_BUG_ON(id >= I915_NUM_ENGINES);
 
 	engine = kzalloc(sizeof(*engine) + PAGE_SIZE, GFP_KERNEL);
 	if (!engine)
@@ -141,7 +143,7 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
 	/* minimal engine setup for requests */
 	engine->base.i915 = i915;
 	snprintf(engine->base.name, sizeof(engine->base.name), "%s", name);
-	engine->base.id = id++;
+	engine->base.id = id;
 	engine->base.status_page.page_addr = (void *)(engine + 1);
 
 	engine->base.context_pin = mock_context_pin;

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

@@ -40,7 +40,8 @@ struct mock_engine {
 };
 
 struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
-				    const char *name);
+				    const char *name,
+				    int id);
 void mock_engine_flush(struct intel_engine_cs *engine);
 void mock_engine_reset(struct intel_engine_cs *engine);
 void mock_engine_free(struct intel_engine_cs *engine);

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

@@ -226,7 +226,7 @@ struct drm_i915_private *mock_gem_device(void)
 	mutex_unlock(&i915->drm.struct_mutex);
 
 	mkwrite_device_info(i915)->ring_mask = BIT(0);
-	i915->engine[RCS] = mock_engine(i915, "mock");
+	i915->engine[RCS] = mock_engine(i915, "mock", RCS);
 	if (!i915->engine[RCS])
 		goto err_priorities;