[PATCH 2/6] drm/i915/guc: Keep guc submission permanently engaged

[Michał Winiarski]

From: Chris Wilson <chris at chris-wilson.co.uk>

We make a decision at module load whether to use the GuC backend or not,
but lose that setup across set-wedge. Currently, the guc doesn't
override the engine->set_default_submission hook letting execlists sneak
back in temporarily on unwedging leading to an unbalanced park/unpark.

v2: Remove comment about switching back temporarily to execlists on
guc_submission_disable(). We currently only call disable on shutdown,
and plan to also call disable before suspend and reset, in which case we
will either restore guc submission or mark the driver as wedged, making
the reset back to execlists pointless.

Testcase: igt/gem_eio
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Michał Winiarski <michal.winiarski at intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
---
 drivers/gpu/drm/i915/intel_guc_submission.c | 37 ++++++++++++++-------
 drivers/gpu/drm/i915/intel_lrc.c            |  2 +-
 drivers/gpu/drm/i915/intel_lrc.h            |  2 ++
 3 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
index 133367a17863..28fd6082603b 100644
--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -1263,6 +1263,29 @@ static void guc_submission_unpark(struct intel_engine_cs *engine)
 	intel_engine_pin_breadcrumbs_irq(engine);
 }
 
+static void guc_set_default_submission(struct intel_engine_cs *engine)
+{
+	/*
+	 * We inherit a bunch of functions from execlists that we'd like
+	 * to keep using:
+	 *
+	 *    engine->submit_request = execlists_submit_request;
+	 *    engine->cancel_requests = execlists_cancel_requests;
+	 *    engine->schedule = execlists_schedule;
+	 *
+	 * But we need to override the actual submission backend in order
+	 * to talk to the GuC.
+	 */
+	execlists_set_default_submission(engine);
+
+	engine->execlists.tasklet.func = guc_submission_tasklet;
+
+	engine->park = guc_submission_park;
+	engine->unpark = guc_submission_unpark;
+
+	engine->flags &= ~I915_ENGINE_SUPPORTS_STATS;
+}
+
 int intel_guc_submission_enable(struct intel_guc *guc)
 {
 	struct drm_i915_private *dev_priv = guc_to_i915(guc);
@@ -1301,17 +1324,10 @@ int intel_guc_submission_enable(struct intel_guc *guc)
 	guc_interrupts_capture(dev_priv);
 
 	for_each_engine(engine, dev_priv, id) {
-		struct intel_engine_execlists * const execlists =
-			&engine->execlists;
-
-		execlists->tasklet.func = guc_submission_tasklet;
-
 		engine->reset.prepare = guc_reset_prepare;
+		engine->set_default_submission = guc_set_default_submission;
 
-		engine->park = guc_submission_park;
-		engine->unpark = guc_submission_unpark;
-
-		engine->flags &= ~I915_ENGINE_SUPPORTS_STATS;
+		engine->set_default_submission(engine);
 	}
 
 	return 0;
@@ -1325,9 +1341,6 @@ void intel_guc_submission_disable(struct intel_guc *guc)
 
 	guc_interrupts_release(dev_priv);
 	guc_clients_doorbell_fini(guc);
-
-	/* Revert back to manual ELSP submission */
-	intel_engines_reset_default_submission(dev_priv);
 }
 
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 517e92c6a70b..35e6312e1d7b 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2324,7 +2324,7 @@ void intel_logical_ring_cleanup(struct intel_engine_cs *engine)
 	kfree(engine);
 }
 
-static void execlists_set_default_submission(struct intel_engine_cs *engine)
+void execlists_set_default_submission(struct intel_engine_cs *engine)
 {
 	engine->submit_request = execlists_submit_request;
 	engine->cancel_requests = execlists_cancel_requests;
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 1593194e930c..8a39c710960a 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -104,4 +104,6 @@ struct i915_gem_context;
 
 void intel_lr_context_resume(struct drm_i915_private *dev_priv);
 
+void execlists_set_default_submission(struct intel_engine_cs *engine);
+
 #endif /* _INTEL_LRC_H_ */
-- 
2.17.0