drm/i915: Prepare i915_gem_active for annotations

In the future, we will want to add annotations to the i915_gem_active
struct. The API is thus expanded to hide direct access to the contents
of i915_gem_active and mediated instead through a number of helpers.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470293567-10811-11-git-send-email-chris@chris-wilson.co.uk

8 files changed, 204 insertions, 66 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 6151460f848f..24ff7f4bc412 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -155,10 +155,10 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
 		   obj->base.write_domain);
 	for_each_engine_id(engine, dev_priv, id)
 		seq_printf(m, "%x ",
-			   i915_gem_request_get_seqno(obj->last_read[id].request));
+			   i915_gem_active_get_seqno(&obj->last_read[id]));
 	seq_printf(m, "] %x %x%s%s%s",
-		   i915_gem_request_get_seqno(obj->last_write.request),
-		   i915_gem_request_get_seqno(obj->last_fence.request),
+		   i915_gem_active_get_seqno(&obj->last_write),
+		   i915_gem_active_get_seqno(&obj->last_fence),
 		   i915_cache_level_str(to_i915(obj->base.dev), obj->cache_level),
 		   obj->dirty ? " dirty" : "",
 		   obj->madv == I915_MADV_DONTNEED ? " purgeable" : "");
@@ -195,8 +195,11 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
 		*t = '\0';
 		seq_printf(m, " (%s mappable)", s);
 	}
-	if (obj->last_write.request)
-		seq_printf(m, " (%s)", obj->last_write.request->engine->name);
+
+	engine = i915_gem_active_get_engine(&obj->last_write);
+	if (engine)
+		seq_printf(m, " (%s)", engine->name);
+
 	if (obj->frontbuffer_bits)
 		seq_printf(m, " (frontbuffer: 0x%03x)", obj->frontbuffer_bits);
 }
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1478efda2f76..0c158c79f640 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1349,27 +1349,30 @@ int
 i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj,
 			       bool readonly)
 {
+	struct drm_i915_gem_request *request;
 	struct reservation_object *resv;
 	int ret, i;
 
 	if (readonly) {
-		if (obj->last_write.request) {
-			ret = i915_wait_request(obj->last_write.request);
+		request = i915_gem_active_peek(&obj->last_write);
+		if (request) {
+			ret = i915_wait_request(request);
 			if (ret)
 				return ret;
 
-			i = obj->last_write.request->engine->id;
-			if (obj->last_read[i].request == obj->last_write.request)
+			i = request->engine->id;
+			if (i915_gem_active_peek(&obj->last_read[i]) == request)
 				i915_gem_object_retire__read(obj, i);
 			else
 				i915_gem_object_retire__write(obj);
 		}
 	} else {
 		for (i = 0; i < I915_NUM_ENGINES; i++) {
-			if (!obj->last_read[i].request)
+			request = i915_gem_active_peek(&obj->last_read[i]);
+			if (!request)
 				continue;
 
-			ret = i915_wait_request(obj->last_read[i].request);
+			ret = i915_wait_request(request);
 			if (ret)
 				return ret;
 
@@ -1397,9 +1400,9 @@ i915_gem_object_retire_request(struct drm_i915_gem_object *obj,
 {
 	int idx = req->engine->id;
 
-	if (obj->last_read[idx].request == req)
+	if (i915_gem_active_peek(&obj->last_read[idx]) == req)
 		i915_gem_object_retire__read(obj, idx);
-	else if (obj->last_write.request == req)
+	else if (i915_gem_active_peek(&obj->last_write) == req)
 		i915_gem_object_retire__write(obj);
 
 	if (!i915_reset_in_progress(&req->i915->gpu_error))
@@ -1428,20 +1431,20 @@ i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj,
 	if (readonly) {
 		struct drm_i915_gem_request *req;
 
-		req = obj->last_write.request;
+		req = i915_gem_active_get(&obj->last_write);
 		if (req == NULL)
 			return 0;
 
-		requests[n++] = i915_gem_request_get(req);
+		requests[n++] = req;
 	} else {
 		for (i = 0; i < I915_NUM_ENGINES; i++) {
 			struct drm_i915_gem_request *req;
 
-			req = obj->last_read[i].request;
+			req = i915_gem_active_get(&obj->last_read[i]);
 			if (req == NULL)
 				continue;
 
-			requests[n++] = i915_gem_request_get(req);
+			requests[n++] = req;
 		}
 	}
 
@@ -2383,8 +2386,8 @@ void i915_vma_move_to_active(struct i915_vma *vma,
 static void
 i915_gem_object_retire__write(struct drm_i915_gem_object *obj)
 {
-	GEM_BUG_ON(!obj->last_write.request);
-	GEM_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write.request->engine)));
+	GEM_BUG_ON(!i915_gem_active_isset(&obj->last_write));
+	GEM_BUG_ON(!(obj->active & intel_engine_flag(i915_gem_active_get_engine(&obj->last_write))));
 
 	i915_gem_active_set(&obj->last_write, NULL);
 	intel_fb_obj_flush(obj, true, ORIGIN_CS);
@@ -2393,15 +2396,17 @@ i915_gem_object_retire__write(struct drm_i915_gem_object *obj)
 static void
 i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int idx)
 {
+	struct intel_engine_cs *engine;
 	struct i915_vma *vma;
 
-	GEM_BUG_ON(!obj->last_read[idx].request);
+	GEM_BUG_ON(!i915_gem_active_isset(&obj->last_read[idx]));
 	GEM_BUG_ON(!(obj->active & (1 << idx)));
 
 	list_del_init(&obj->engine_list[idx]);
 	i915_gem_active_set(&obj->last_read[idx], NULL);
 
-	if (obj->last_write.request && obj->last_write.request->engine->id == idx)
+	engine = i915_gem_active_get_engine(&obj->last_write);
+	if (engine && engine->id == idx)
 		i915_gem_object_retire__write(obj);
 
 	obj->active &= ~(1 << idx);
@@ -2621,7 +2626,7 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *engine)
 				       struct drm_i915_gem_object,
 				       engine_list[engine->id]);
 
-		if (!list_empty(&obj->last_read[engine->id].request->list))
+		if (!list_empty(&i915_gem_active_peek(&obj->last_read[engine->id])->list))
 			break;
 
 		i915_gem_object_retire__read(obj, engine->id);
@@ -2754,7 +2759,7 @@ i915_gem_object_flush_active(struct drm_i915_gem_object *obj)
 	for (i = 0; i < I915_NUM_ENGINES; i++) {
 		struct drm_i915_gem_request *req;
 
-		req = obj->last_read[i].request;
+		req = i915_gem_active_peek(&obj->last_read[i]);
 		if (req == NULL)
 			continue;
 
@@ -2794,7 +2799,7 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 {
 	struct drm_i915_gem_wait *args = data;
 	struct drm_i915_gem_object *obj;
-	struct drm_i915_gem_request *req[I915_NUM_ENGINES];
+	struct drm_i915_gem_request *requests[I915_NUM_ENGINES];
 	int i, n = 0;
 	int ret;
 
@@ -2830,20 +2835,21 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 	i915_gem_object_put(obj);
 
 	for (i = 0; i < I915_NUM_ENGINES; i++) {
-		if (!obj->last_read[i].request)
-			continue;
+		struct drm_i915_gem_request *req;
 
-		req[n++] = i915_gem_request_get(obj->last_read[i].request);
+		req = i915_gem_active_get(&obj->last_read[i]);
+		if (req)
+			requests[n++] = req;
 	}
 
 	mutex_unlock(&dev->struct_mutex);
 
 	for (i = 0; i < n; i++) {
 		if (ret == 0)
-			ret = __i915_wait_request(req[i], true,
+			ret = __i915_wait_request(requests[i], true,
 						  args->timeout_ns > 0 ? &args->timeout_ns : NULL,
 						  to_rps_client(file));
-		i915_gem_request_put(req[i]);
+		i915_gem_request_put(requests[i]);
 	}
 	return ret;
 
@@ -2916,7 +2922,7 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj,
 		     struct drm_i915_gem_request *to)
 {
 	const bool readonly = obj->base.pending_write_domain == 0;
-	struct drm_i915_gem_request *req[I915_NUM_ENGINES];
+	struct drm_i915_gem_request *requests[I915_NUM_ENGINES];
 	int ret, i, n;
 
 	if (!obj->active)
@@ -2924,15 +2930,22 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj,
 
 	n = 0;
 	if (readonly) {
-		if (obj->last_write.request)
-			req[n++] = obj->last_write.request;
+		struct drm_i915_gem_request *req;
+
+		req = i915_gem_active_peek(&obj->last_write);
+		if (req)
+			requests[n++] = req;
 	} else {
-		for (i = 0; i < I915_NUM_ENGINES; i++)
-			if (obj->last_read[i].request)
-				req[n++] = obj->last_read[i].request;
+		for (i = 0; i < I915_NUM_ENGINES; i++) {
+			struct drm_i915_gem_request *req;
+
+			req = i915_gem_active_peek(&obj->last_read[i]);
+			if (req)
+				requests[n++] = req;
+		}
 	}
 	for (i = 0; i < n; i++) {
-		ret = __i915_gem_object_sync(obj, to, req[i]);
+		ret = __i915_gem_object_sync(obj, to, requests[i]);
 		if (ret)
 			return ret;
 	}
@@ -4021,17 +4034,17 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
 
 	args->busy = 0;
 	if (obj->active) {
+		struct drm_i915_gem_request *req;
 		int i;
 
 		for (i = 0; i < I915_NUM_ENGINES; i++) {
-			struct drm_i915_gem_request *req;
-
-			req = obj->last_read[i].request;
+			req = i915_gem_active_peek(&obj->last_read[i]);
 			if (req)
 				args->busy |= 1 << (16 + req->engine->exec_id);
 		}
-		if (obj->last_write.request)
-			args->busy |= obj->last_write.request->engine->exec_id;
+		req = i915_gem_active_peek(&obj->last_write);
+		if (req)
+			args->busy |= req->engine->exec_id;
 	}
 
 unref:
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
index d16b385e79e9..9fdbd66128a6 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -261,14 +261,13 @@ static inline void i915_gem_object_fence_lost(struct drm_i915_gem_object *obj)
 static int
 i915_gem_object_wait_fence(struct drm_i915_gem_object *obj)
 {
-	if (obj->last_fence.request) {
-		int ret = i915_wait_request(obj->last_fence.request);
-		if (ret)
-			return ret;
+	int ret;
 
-		i915_gem_active_set(&obj->last_fence, NULL);
-	}
+	ret = i915_gem_active_wait(&obj->last_fence);
+	if (ret)
+		return ret;
 
+	i915_gem_active_set(&obj->last_fence, NULL);
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
index cf2df33f9892..e13834e2e3e0 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.h
+++ b/drivers/gpu/drm/i915/i915_gem_request.h
@@ -280,6 +280,15 @@ struct i915_gem_active {
 	struct drm_i915_gem_request *request;
 };
 
+/**
+ * i915_gem_active_set - updates the tracker to watch the current request
+ * @active - the active tracker
+ * @request - the request to watch
+ *
+ * i915_gem_active_set() watches the given @request for completion. Whilst
+ * that @request is busy, the @active reports busy. When that @request is
+ * retired, the @active tracker is updated to report idle.
+ */
 static inline void
 i915_gem_active_set(struct i915_gem_active *active,
 		    struct drm_i915_gem_request *request)
@@ -287,6 +296,124 @@ i915_gem_active_set(struct i915_gem_active *active,
 	i915_gem_request_assign(&active->request, request);
 }
 
+/**
+ * i915_gem_active_peek - report the request being monitored
+ * @active - the active tracker
+ *
+ * i915_gem_active_peek() returns the current request being tracked, or NULL.
+ * It does not obtain a reference on the request for the caller, so the
+ * caller must hold struct_mutex.
+ */
+static inline struct drm_i915_gem_request *
+i915_gem_active_peek(const struct i915_gem_active *active)
+{
+	return active->request;
+}
+
+/**
+ * i915_gem_active_get - return a reference to the active request
+ * @active - the active tracker
+ *
+ * i915_gem_active_get() returns a reference to the active request, or NULL
+ * if the active tracker is idle. The caller must hold struct_mutex.
+ */
+static inline struct drm_i915_gem_request *
+i915_gem_active_get(const struct i915_gem_active *active)
+{
+	struct drm_i915_gem_request *request;
+
+	request = i915_gem_active_peek(active);
+	if (!request || i915_gem_request_completed(request))
+		return NULL;
+
+	return i915_gem_request_get(request);
+}
+
+/**
+ * i915_gem_active_isset - report whether the active tracker is assigned
+ * @active - the active tracker
+ *
+ * i915_gem_active_isset() returns true if the active tracker is currently
+ * assigned to a request. Due to the lazy retiring, that request may be idle
+ * and this may report stale information.
+ */
+static inline bool
+i915_gem_active_isset(const struct i915_gem_active *active)
+{
+	return active->request;
+}
+
+/**
+ * i915_gem_active_is_idle - report whether the active tracker is idle
+ * @active - the active tracker
+ *
+ * i915_gem_active_is_idle() returns true if the active tracker is currently
+ * unassigned or if the request is complete (but not yet retired). Requires
+ * the caller to hold struct_mutex (but that can be relaxed if desired).
+ */
+static inline bool
+i915_gem_active_is_idle(const struct i915_gem_active *active)
+{
+	struct drm_i915_gem_request *request;
+
+	request = i915_gem_active_peek(active);
+	if (!request || i915_gem_request_completed(request))
+		return true;
+
+	return false;
+}
+
+/**
+ * i915_gem_active_wait - waits until the request is completed
+ * @active - the active request on which to wait
+ *
+ * i915_gem_active_wait() waits until the request is completed before
+ * returning. Note that it does not guarantee that the request is
+ * retired first, see i915_gem_active_retire().
+ */
+static inline int __must_check
+i915_gem_active_wait(const struct i915_gem_active *active)
+{
+	struct drm_i915_gem_request *request;
+
+	request = i915_gem_active_peek(active);
+	if (!request)
+		return 0;
+
+	return i915_wait_request(request);
+}
+
+/**
+ * i915_gem_active_retire - waits until the request is retired
+ * @active - the active request on which to wait
+ *
+ * i915_gem_active_retire() waits until the request is completed,
+ * and then ensures that at least the retirement handler for this
+ * @active tracker is called before returning. If the @active
+ * tracker is idle, the function returns immediately.
+ */
+static inline int __must_check
+i915_gem_active_retire(const struct i915_gem_active *active)
+{
+	return i915_gem_active_wait(active);
+}
+
+/* Convenience functions for peeking at state inside active's request whilst
+ * guarded by the struct_mutex.
+ */
+
+static inline uint32_t
+i915_gem_active_get_seqno(const struct i915_gem_active *active)
+{
+	return i915_gem_request_get_seqno(i915_gem_active_peek(active));
+}
+
+static inline struct intel_engine_cs *
+i915_gem_active_get_engine(const struct i915_gem_active *active)
+{
+	return i915_gem_request_get_engine(i915_gem_active_peek(active));
+}
+
 #define for_each_active(mask, idx) \
 	for (; mask ? idx = ffs(mask) - 1, 1 : 0; mask &= ~BIT(idx))
 
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index 00d796da65fb..8cef2d6b291a 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -242,7 +242,7 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
 			}
 
 			obj->fence_dirty =
-				obj->last_fence.request ||
+				!i915_gem_active_is_idle(&obj->last_fence) ||
 				obj->fence_reg != I915_FENCE_REG_NONE;
 
 			obj->tiling_mode = args->tiling_mode;
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 32f50a70ea42..00ab5e9d2eb7 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -74,11 +74,9 @@ static void wait_rendering(struct drm_i915_gem_object *obj)
 	for (i = 0; i < I915_NUM_ENGINES; i++) {
 		struct drm_i915_gem_request *req;
 
-		req = obj->last_read[i].request;
-		if (req == NULL)
-			continue;
-
-		requests[n++] = i915_gem_request_get(req);
+		req = i915_gem_active_get(&obj->last_read[i]);
+		if (req)
+			requests[n++] = req;
 	}
 
 	mutex_unlock(&dev->struct_mutex);
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index d6482e980d5e..585fe2bdadd5 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -746,13 +746,14 @@ static void capture_bo(struct drm_i915_error_buffer *err,
 		       struct i915_vma *vma)
 {
 	struct drm_i915_gem_object *obj = vma->obj;
+	struct intel_engine_cs *engine;
 	int i;
 
 	err->size = obj->base.size;
 	err->name = obj->base.name;
 	for (i = 0; i < I915_NUM_ENGINES; i++)
-		err->rseqno[i] = i915_gem_request_get_seqno(obj->last_read[i].request);
-	err->wseqno = i915_gem_request_get_seqno(obj->last_write.request);
+		err->rseqno[i] = i915_gem_active_get_seqno(&obj->last_read[i]);
+	err->wseqno = i915_gem_active_get_seqno(&obj->last_write);
 	err->gtt_offset = vma->node.start;
 	err->read_domains = obj->base.read_domains;
 	err->write_domain = obj->base.write_domain;
@@ -764,8 +765,10 @@ static void capture_bo(struct drm_i915_error_buffer *err,
 	err->dirty = obj->dirty;
 	err->purgeable = obj->madv != I915_MADV_WILLNEED;
 	err->userptr = obj->userptr.mm != NULL;
-	err->engine = obj->last_write.request ? obj->last_write.request->engine->id : -1;
 	err->cache_level = obj->cache_level;
+
+	engine = i915_gem_active_get_engine(&obj->last_write);
+	err->engine = engine ? engine->id : -1;
 }
 
 static u32 capture_active_bo(struct drm_i915_error_buffer *err,
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index e858fede37ce..8c03d13d494d 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11370,7 +11370,7 @@ static bool use_mmio_flip(struct intel_engine_cs *engine,
 	if (resv && !reservation_object_test_signaled_rcu(resv, false))
 		return true;
 
-	return engine != i915_gem_request_get_engine(obj->last_write.request);
+	return engine != i915_gem_active_get_engine(&obj->last_write);
 }
 
 static void skl_do_mmio_flip(struct intel_crtc *intel_crtc,
@@ -11673,7 +11673,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 	} else if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev)) {
 		engine = &dev_priv->engine[BCS];
 	} else if (INTEL_INFO(dev)->gen >= 7) {
-		engine = i915_gem_request_get_engine(obj->last_write.request);
+		engine = i915_gem_active_get_engine(&obj->last_write);
 		if (engine == NULL || engine->id != RCS)
 			engine = &dev_priv->engine[BCS];
 	} else {
@@ -11694,9 +11694,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 	if (mmio_flip) {
 		INIT_WORK(&work->mmio_work, intel_mmio_flip_work_func);
 
-		i915_gem_request_assign(&work->flip_queued_req,
-					obj->last_write.request);
-
+		work->flip_queued_req = i915_gem_active_get(&obj->last_write);
 		schedule_work(&work->mmio_work);
 	} else {
 		request = i915_gem_request_alloc(engine, engine->last_context);
@@ -14039,11 +14037,8 @@ intel_prepare_plane_fb(struct drm_plane *plane,
 	}
 
 	if (ret == 0) {
-		struct intel_plane_state *plane_state =
-			to_intel_plane_state(new_state);
-
-		i915_gem_request_assign(&plane_state->wait_req,
-					obj->last_write.request);
+		to_intel_plane_state(new_state)->wait_req =
+			i915_gem_active_get(&obj->last_write);
 	}
 
 	return ret;