[PATCH 1/3] drm/i915: Refactor wakeup of the next breadcrumb waiter

[Chris Wilson]

Since extracting the reset wakeup into a independent waitqueue, we only
need to consider the possibility of there being an outstanding
breadcrumb interrupt when advancing onto the next waiter. Both paths can
now use the same code, so refactor it to a common function.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_breadcrumbs.c | 56 +++++++++++++++-----------------
 1 file changed, 27 insertions(+), 29 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index 235d4645a5cf..afefacc2e226 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -287,6 +287,29 @@ static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b,
 	wake_up_process(wait->tsk); /* implicit smp_wmb() */
 }
 
+static inline void __intel_breadcrumbs_next(struct intel_engine_cs *engine,
+					    struct rb_node *next)
+{
+	struct intel_breadcrumbs *b = &engine->breadcrumbs;
+
+	/* As there is a delay between reading the current
+	 * seqno, processing the completed tasks and selecting
+	 * the next waiter, we may have missed the interrupt
+	 * and so need for the next bottom-half to wakeup.
+	 *
+	 * Note that we only have to consider wake ups from the interrupt
+	 * (breadcrumb completion) here as any others (such as GPU reset) will
+	 * wake up the affect processes directly.
+	 */
+
+	GEM_BUG_ON(!b->irq_armed);
+	b->first_wait = to_wait(next);
+
+	if (engine->irq_seqno_barrier &&
+	    test_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted))
+		wake_up_process(to_wait(next)->tsk);
+}
+
 static bool __intel_engine_add_wait(struct intel_engine_cs *engine,
 				    struct intel_wait *wait)
 {
@@ -357,21 +380,7 @@ static bool __intel_engine_add_wait(struct intel_engine_cs *engine,
 		GEM_BUG_ON(!next && !first);
 		if (next && next != &wait->node) {
 			GEM_BUG_ON(first);
-			b->first_wait = to_wait(next);
-			/* As there is a delay between reading the current
-			 * seqno, processing the completed tasks and selecting
-			 * the next waiter, we may have missed the interrupt
-			 * and so need for the next bottom-half to wakeup.
-			 *
-			 * Also as we enable the IRQ, we may miss the
-			 * interrupt for that seqno, so we have to wake up
-			 * the next bottom-half in order to do a coherent check
-			 * in case the seqno passed.
-			 */
-			__intel_breadcrumbs_enable_irq(b);
-			if (test_bit(ENGINE_IRQ_BREADCRUMB,
-				     &engine->irq_posted))
-				wake_up_process(to_wait(next)->tsk);
+			__intel_breadcrumbs_next(engine, next);
 		}
 
 		do {
@@ -473,21 +482,10 @@ static void __intel_engine_remove_wait(struct intel_engine_cs *engine,
 			}
 		}
 
-		if (next) {
-			/* In our haste, we may have completed the first waiter
-			 * before we enabled the interrupt. Do so now as we
-			 * have a second waiter for a future seqno. Afterwards,
-			 * we have to wake up that waiter in case we missed
-			 * the interrupt, or if we have to handle an
-			 * exception rather than a seqno completion.
-			 */
-			b->first_wait = to_wait(next);
-			if (b->first_wait->seqno != wait->seqno)
-				__intel_breadcrumbs_enable_irq(b);
-			wake_up_process(b->first_wait->tsk);
-		} else {
+		if (next)
+			__intel_breadcrumbs_next(engine, next);
+		else
 			b->first_wait = NULL;
-		}
 	} else {
 		GEM_BUG_ON(rb_first(&b->waiters) == &wait->node);
 	}
-- 
2.11.0