[PATCH 4/5] drm/i915: Park before resetting the submission backend

[Chris Wilson]

As different backends may have different park/unpark callbacks, we
should only ever switch backends (reset_default_submission on wedge
recovery, or on enabling the guc) while parked.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c             | 11 +++++++++++
 drivers/gpu/drm/i915/intel_engine_cs.c      |  3 +++
 drivers/gpu/drm/i915/intel_guc_submission.c |  1 +
 3 files changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e148db310ea6..e2880de2fc7e 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3380,6 +3380,17 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
 	i915_retire_requests(i915);
 	GEM_BUG_ON(i915->gt.active_requests);
 
+	/*
+	 * Park before disengaging the old submit mechanism as different
+	 * backends may have different park/unpack callbacks.
+	 *
+	 * We are idle; the idle-worker will be queued, but we need to run
+	 * it now. As we already hold the struct mutex, we can get park
+	 * the GPU right away, letting the lazy worker see that we are
+	 * already active again by the time it acquires the mutex.
+	 */
+	i915_gem_park(i915);
+
 	/*
 	 * Undo nop_submit_request. We prevent all new i915 requests from
 	 * being queued (by disallowing execbuf whilst wedged) so having
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 12486d8f534b..b4ea77a2896c 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1651,6 +1651,9 @@ void intel_engines_reset_default_submission(struct drm_i915_private *i915)
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
 
+	/* Must be parked first! */
+	GEM_BUG_ON(i915->gt.awake);
+
 	for_each_engine(engine, i915, id)
 		engine->set_default_submission(engine);
 }
diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
index 97121230656c..225fa3927a02 100644
--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -1243,6 +1243,7 @@ int intel_guc_submission_enable(struct intel_guc *guc)
 	/* Take over from manual control of ELSP (execlists) */
 	guc_interrupts_capture(dev_priv);
 
+	GEM_BUG_ON(dev_priv->gt.awake); /* Must be idle switching park/unpark */
 	for_each_engine(engine, dev_priv, id) {
 		struct intel_engine_execlists * const execlists =
 			&engine->execlists;
-- 
2.16.3