[Intel-gfx] [PATCH] drm/i915/guc: keep breadcrumb irq always enabled

[Daniele Ceraolo Spurio]

We rely on the tasklet to update the GT PM refcount, so we can't disable
it even if we've processed all the requests for the engine because we
might have detected the request completion before the interrupt arrived.

Since on all platforms on which we plan to support guc submission we
don't allow disabling the breadcrumb interrupts, we can further siplify
the park/unpark flow by removing the interrupt pin/unpin. A BUG_ON has
been added to catch changes to this flow that would require us to
restore some kind of pinning.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_breadcrumbs.c   | 22 ----------------
 drivers/gpu/drm/i915/gt/intel_engine.h        |  3 ---
 .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 25 ++++++++-----------
 3 files changed, 11 insertions(+), 39 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index ceba1da61967..15bbdd8c7552 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -212,28 +212,6 @@ static void signal_irq_work(struct irq_work *work)
 	intel_engine_breadcrumbs_irq(engine);
 }
 
-void intel_engine_pin_breadcrumbs_irq(struct intel_engine_cs *engine)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-
-	spin_lock_irq(&b->irq_lock);
-	if (!b->irq_enabled++)
-		irq_enable(engine);
-	GEM_BUG_ON(!b->irq_enabled); /* no overflow! */
-	spin_unlock_irq(&b->irq_lock);
-}
-
-void intel_engine_unpin_breadcrumbs_irq(struct intel_engine_cs *engine)
-{
-	struct intel_breadcrumbs *b = &engine->breadcrumbs;
-
-	spin_lock_irq(&b->irq_lock);
-	GEM_BUG_ON(!b->irq_enabled); /* no underflow! */
-	if (!--b->irq_enabled)
-		irq_disable(engine);
-	spin_unlock_irq(&b->irq_lock);
-}
-
 static void __intel_breadcrumbs_arm_irq(struct intel_breadcrumbs *b)
 {
 	struct intel_engine_cs *engine =
diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
index e1228b0e577f..bc694adcd9ea 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -338,9 +338,6 @@ void intel_engine_init_execlists(struct intel_engine_cs *engine);
 void intel_engine_init_breadcrumbs(struct intel_engine_cs *engine);
 void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine);
 
-void intel_engine_pin_breadcrumbs_irq(struct intel_engine_cs *engine);
-void intel_engine_unpin_breadcrumbs_irq(struct intel_engine_cs *engine);
-
 void intel_engine_signal_breadcrumbs(struct intel_engine_cs *engine);
 void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine);
 
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index 449ca6357018..deb054eeb37c 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -1059,18 +1059,6 @@ static void guc_interrupts_release(struct intel_gt *gt)
 	rps->pm_intrmsk_mbz &= ~ARAT_EXPIRED_INTRMSK;
 }
 
-static void guc_submission_park(struct intel_engine_cs *engine)
-{
-	intel_engine_unpin_breadcrumbs_irq(engine);
-	engine->flags &= ~I915_ENGINE_NEEDS_BREADCRUMB_TASKLET;
-}
-
-static void guc_submission_unpark(struct intel_engine_cs *engine)
-{
-	engine->flags |= I915_ENGINE_NEEDS_BREADCRUMB_TASKLET;
-	intel_engine_pin_breadcrumbs_irq(engine);
-}
-
 static void guc_set_default_submission(struct intel_engine_cs *engine)
 {
 	/*
@@ -1088,8 +1076,8 @@ static void guc_set_default_submission(struct intel_engine_cs *engine)
 
 	engine->execlists.tasklet.func = guc_submission_tasklet;
 
-	engine->park = guc_submission_park;
-	engine->unpark = guc_submission_unpark;
+	/* do not use execlists park/unpark */
+	engine->park = engine->unpark = NULL;
 
 	engine->reset.prepare = guc_reset_prepare;
 	engine->reset.reset = guc_reset;
@@ -1098,6 +1086,15 @@ static void guc_set_default_submission(struct intel_engine_cs *engine)
 	engine->cancel_requests = guc_cancel_requests;
 
 	engine->flags &= ~I915_ENGINE_SUPPORTS_STATS;
+	engine->flags |= I915_ENGINE_NEEDS_BREADCRUMB_TASKLET;
+
+	/*
+	 * For the breadcrumb irq to work we need the interrupts to stay
+	 * enabled. However, on all platforms on which we'll have support for
+	 * GuC submission we don't allow disabling the interrupts at runtime, so
+	 * we're always safe with the current flow.
+	 */
+	GEM_BUG_ON(engine->irq_enable || engine->irq_disable);
 }
 
 int intel_guc_submission_enable(struct intel_guc *guc)
-- 
2.22.0