[PATCH v2] drm/i915: Convert trace-irq to the breadcrumb waiter

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If we convert the tracing over from direct use of ring->irq_get() and
over to the breadcrumb infrastructure, we only have a single user of the
ring->irq_get and so we will be able to simplify the driver routines
(eliminating the redundant validation and irq refcounting).

v2: Move to a signalling framework based upon the waiter.

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_drv.h          |   8 --
 drivers/gpu/drm/i915/i915_gem.c          |   6 --
 drivers/gpu/drm/i915/i915_trace.h        |   2 +-
 drivers/gpu/drm/i915/intel_breadcrumbs.c | 132 +++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_ringbuffer.h  |   6 +-
 5 files changed, 138 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 37f4ef59fb4a..dabfb043362f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3625,12 +3625,4 @@ wait_remaining_ms_from_jiffies(unsigned long timestamp_jiffies, int to_wait_ms)
 			    schedule_timeout_uninterruptible(remaining_jiffies);
 	}
 }
-
-static inline void i915_trace_irq_get(struct intel_engine_cs *ring,
-				      struct drm_i915_gem_request *req)
-{
-	if (ring->trace_irq_req == NULL && ring->irq_get(ring))
-		i915_gem_request_assign(&ring->trace_irq_req, req);
-}
-
 #endif
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1ef677f3aac8..550ccd7873ab 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2907,12 +2907,6 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *ring)
 		i915_gem_object_retire__read(obj, ring->id);
 	}
 
-	if (unlikely(ring->trace_irq_req &&
-		     i915_gem_request_completed(ring->trace_irq_req))) {
-		ring->irq_put(ring);
-		i915_gem_request_assign(&ring->trace_irq_req, NULL);
-	}
-
 	WARN_ON(i915_verify_lists(ring->dev));
 }
 
diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
index efca75bcace3..3446abb4cf59 100644
--- a/drivers/gpu/drm/i915/i915_trace.h
+++ b/drivers/gpu/drm/i915/i915_trace.h
@@ -503,7 +503,7 @@ TRACE_EVENT(i915_gem_ring_dispatch,
 			   __entry->ring = ring->id;
 			   __entry->seqno = i915_gem_request_get_seqno(req);
 			   __entry->flags = flags;
-			   i915_trace_irq_get(ring, req);
+			   intel_engine_add_signal(req);
 			   ),
 
 	    TP_printk("dev=%u, ring=%u, seqno=%u, flags=%x",
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index aefea0bf8a32..faf082b43202 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -22,6 +22,8 @@
  *
  */
 
+#include <linux/kthread.h>
+
 #include "i915_drv.h"
 
 static void intel_breadcrumbs_fake_irq(unsigned long data)
@@ -266,9 +268,139 @@ void intel_engine_init_breadcrumbs(struct intel_engine_cs *engine)
 	setup_timer(&b->fake_irq, intel_breadcrumbs_fake_irq, (unsigned long)b);
 }
 
+struct signal {
+	struct rb_node node;
+	struct intel_wait wait;
+	struct drm_i915_gem_request *request;
+};
+
+static bool signal_complete(struct signal *signal)
+{
+	struct drm_i915_gem_request *rq = signal->request;
+
+	if (signal == NULL)
+		return false;
+
+	if (intel_wait_complete(&signal->wait))
+		return true;
+
+	if (i915_gem_request_completed(rq))
+		return true;
+
+	if (rq->ring->seqno_barrier) {
+		rq->ring->seqno_barrier(rq->ring);
+		if (i915_gem_request_completed(rq))
+			return true;
+	}
+
+	if (rq->reset_counter != i915_reset_counter(&rq->i915->gpu_error))
+		return true;
+
+	return false;
+}
+
+static struct signal *to_signal(struct rb_node *rb)
+{
+	return container_of(rb, struct signal, node);
+}
+
+static int intel_breadcrumbs_signaller(void *arg)
+{
+	struct intel_engine_cs *engine = arg;
+
+	do {
+		struct signal *signal;
+
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		spin_lock(&engine->breadcrumbs.lock);
+		signal = to_signal(rb_first(&engine->breadcrumbs.signals));
+		spin_unlock(&engine->breadcrumbs.lock);
+
+		if (signal_complete(signal)) {
+			intel_engine_remove_wait(engine, &signal->wait);
+
+			i915_gem_request_unreference__unlocked(signal->request);
+
+			spin_lock(&engine->breadcrumbs.lock);
+			rb_erase(&signal->node, &engine->breadcrumbs.signals);
+			spin_unlock(&engine->breadcrumbs.lock);
+
+			kfree(signal);
+		} else {
+			i915_queue_hangcheck(engine->i915);
+
+			if (kthread_should_stop())
+				break;
+
+			schedule();
+		}
+	} while (1);
+
+	return 0;
+}
+
+int intel_engine_add_signal(struct drm_i915_gem_request *request)
+{
+	struct intel_engine_cs *engine = request->ring;
+	struct intel_breadcrumbs *b = &engine->breadcrumbs;
+	struct rb_node *parent, **p;
+	struct task_struct *task;
+	struct signal *signal;
+
+	signal = kmalloc(sizeof(*signal), GFP_ATOMIC);
+	if (signal == NULL)
+		return -ENOMEM;
+
+	task = READ_ONCE(b->signaller);
+	if (task == NULL) {
+		spin_lock(&b->lock);
+		task = kthread_create(intel_breadcrumbs_signaller,
+				      engine, "irq/i915-%d", engine->id);
+		if (!IS_ERR(task))
+			b->signaller = task;
+		spin_unlock(&b->lock);
+
+		if (IS_ERR(task)) {
+			kfree(signal);
+			return PTR_ERR(task);
+		}
+	}
+
+	signal->wait.task = task;
+	signal->wait.seqno = request->seqno;
+
+	signal->request = i915_gem_request_reference(request);
+
+	spin_lock(&b->lock);
+	parent = NULL;
+	p = &b->signals.rb_node;
+	while (*p) {
+		parent = *p;
+		if (i915_seqno_passed(signal->wait.seqno,
+				      to_signal(parent)->wait.seqno))
+			p = &parent->rb_right;
+		else
+			p = &parent->rb_left;
+	}
+	rb_link_node(&signal->node, parent, p);
+	rb_insert_color(&signal->node, &b->signals);
+	spin_unlock(&b->lock);
+
+	if (intel_engine_add_wait(engine, &signal->wait)) {
+		intel_engine_enable_irq(engine);
+		wake_up_process(task);
+	}
+
+	return 0;
+}
+
 void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
 {
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;
 
+	if (b->signaller)
+		kthread_stop(b->signaller);
+
 	del_timer_sync(&b->fake_irq);
 }
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 3c390ce26919..cff3f15f9859 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -144,6 +144,8 @@ struct  i915_ctx_workarounds {
 	struct drm_i915_gem_object *obj;
 };
 
+struct drm_i915_gem_request;
+
 struct  intel_engine_cs {
 	const char	*name;
 	enum intel_ring_id {
@@ -180,7 +182,9 @@ struct  intel_engine_cs {
 	struct intel_breadcrumbs {
 		spinlock_t lock; /* protects the lists of requests */
 		struct rb_root waiters; /* sorted by retirement */
+		struct rb_root signals; /* sorted by retirement */
 		struct task_struct *first_waiter; /* bh for user interrupts */
+		struct task_struct *signaller; /* used for fence signalling */
 		struct timer_list fake_irq; /* used after a missed interrupt */
 		bool irq_enabled;
 		bool rpm_wakelock;
@@ -198,7 +202,6 @@ struct  intel_engine_cs {
 
 	unsigned irq_refcount; /* protected by dev_priv->irq_lock */
 	u32		irq_enable_mask;	/* bitmask to enable ring interrupt */
-	struct drm_i915_gem_request *trace_irq_req;
 	bool __must_check (*irq_get)(struct intel_engine_cs *ring);
 	void		(*irq_put)(struct intel_engine_cs *ring);
 
@@ -554,6 +557,7 @@ bool intel_engine_add_wait(struct intel_engine_cs *engine,
 			   struct intel_wait *wait);
 void intel_engine_remove_wait(struct intel_engine_cs *engine,
 			      struct intel_wait *wait);
+int intel_engine_add_signal(struct drm_i915_gem_request *request);
 static inline bool intel_engine_has_waiter(struct intel_engine_cs *engine)
 {
 	return READ_ONCE(engine->breadcrumbs.first_waiter);
-- 
2.6.3

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