[PATCH v2] drm/i915: Introduce drm_i915_gem_request_active for request tracking

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In the next patch, request tracking is made more generic and for that we
need a new expanded struct and to separate out the logic changes from
the mechanical churn, we split out the structure renaming into this
patch.

v2: Writer's block. Add some spiel about why we track requests.

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_debugfs.c        | 10 +++---
 drivers/gpu/drm/i915/i915_drv.h            |  9 +++--
 drivers/gpu/drm/i915/i915_gem.c            | 56 +++++++++++++++---------------
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |  4 +--
 drivers/gpu/drm/i915/i915_gem_fence.c      |  6 ++--
 drivers/gpu/drm/i915/i915_gem_request.h    | 37 ++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem_tiling.c     |  2 +-
 drivers/gpu/drm/i915/i915_gpu_error.c      |  6 ++--
 drivers/gpu/drm/i915/intel_display.c       | 10 +++---
 9 files changed, 88 insertions(+), 52 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 77bae3151fca..dafc58b94c9f 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -146,10 +146,10 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
 		   obj->base.write_domain);
 	for_each_ring(ring, dev_priv, i)
 		seq_printf(m, "%x ",
-				i915_gem_request_get_seqno(obj->last_read_req[i]));
+				i915_gem_request_get_seqno(obj->last_read[i].request));
 	seq_printf(m, "] %x %x%s%s%s",
-		   i915_gem_request_get_seqno(obj->last_write_req),
-		   i915_gem_request_get_seqno(obj->last_fenced_req),
+		   i915_gem_request_get_seqno(obj->last_write.request),
+		   i915_gem_request_get_seqno(obj->last_fence.request),
 		   i915_cache_level_str(to_i915(obj->base.dev), obj->cache_level),
 		   obj->dirty ? " dirty" : "",
 		   obj->madv == I915_MADV_DONTNEED ? " purgeable" : "");
@@ -184,8 +184,8 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
 		*t = '\0';
 		seq_printf(m, " (%s mappable)", s);
 	}
-	if (obj->last_write_req != NULL)
-		seq_printf(m, " (%s)", obj->last_write_req->engine->name);
+	if (obj->last_write.request != NULL)
+		seq_printf(m, " (%s)", obj->last_write.request->engine->name);
 	if (obj->frontbuffer_bits)
 		seq_printf(m, " (frontbuffer: 0x%03x)", obj->frontbuffer_bits);
 }
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 426a0eade0f8..49ef9b04456e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2102,11 +2102,10 @@ struct drm_i915_gem_object {
 	 * requests on one ring where the write request is older than the
 	 * read request. This allows for the CPU to read from an active
 	 * buffer by only waiting for the write to complete.
-	 * */
-	struct drm_i915_gem_request *last_read_req[I915_NUM_RINGS];
-	struct drm_i915_gem_request *last_write_req;
-	/** Breadcrumb of last fenced GPU access to the buffer. */
-	struct drm_i915_gem_request *last_fenced_req;
+	 */
+	struct drm_i915_gem_request_active last_read[I915_NUM_RINGS];
+	struct drm_i915_gem_request_active last_write;
+	struct drm_i915_gem_request_active last_fence;
 
 	/** Current tiling stride for the object, if it's tiled. */
 	uint32_t stride;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e85fd7746171..d46dc7f348a0 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1119,23 +1119,23 @@ i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj,
 		return 0;
 
 	if (readonly) {
-		if (obj->last_write_req != NULL) {
-			ret = i915_wait_request(obj->last_write_req);
+		if (obj->last_write.request != NULL) {
+			ret = i915_wait_request(obj->last_write.request);
 			if (ret)
 				return ret;
 
-			i = obj->last_write_req->engine->id;
-			if (obj->last_read_req[i] == obj->last_write_req)
+			i = obj->last_write.request->engine->id;
+			if (obj->last_read[i].request == obj->last_write.request)
 				i915_gem_object_retire__read(obj, i);
 			else
 				i915_gem_object_retire__write(obj);
 		}
 	} else {
 		for (i = 0; i < I915_NUM_RINGS; i++) {
-			if (obj->last_read_req[i] == NULL)
+			if (obj->last_read[i].request == NULL)
 				continue;
 
-			ret = i915_wait_request(obj->last_read_req[i]);
+			ret = i915_wait_request(obj->last_read[i].request);
 			if (ret)
 				return ret;
 
@@ -1153,9 +1153,9 @@ i915_gem_object_retire_request(struct drm_i915_gem_object *obj,
 {
 	int ring = req->engine->id;
 
-	if (obj->last_read_req[ring] == req)
+	if (obj->last_read[ring].request == req)
 		i915_gem_object_retire__read(obj, ring);
-	else if (obj->last_write_req == req)
+	else if (obj->last_write.request == req)
 		i915_gem_object_retire__write(obj);
 
 	i915_gem_request_retire_upto(req);
@@ -1183,7 +1183,7 @@ i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj,
 	if (readonly) {
 		struct drm_i915_gem_request *req;
 
-		req = obj->last_write_req;
+		req = obj->last_write.request;
 		if (req == NULL)
 			return 0;
 
@@ -1192,7 +1192,7 @@ i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj,
 		for (i = 0; i < I915_NUM_RINGS; i++) {
 			struct drm_i915_gem_request *req;
 
-			req = obj->last_read_req[i];
+			req = obj->last_read[i].request;
 			if (req == NULL)
 				continue;
 
@@ -2062,7 +2062,7 @@ void i915_vma_move_to_active(struct i915_vma *vma,
 	obj->active |= intel_engine_flag(engine);
 
 	list_move_tail(&obj->ring_list[engine->id], &engine->active_list);
-	i915_gem_request_assign(&obj->last_read_req[engine->id], req);
+	i915_gem_request_mark_active(req, &obj->last_read[engine->id]);
 
 	list_move_tail(&vma->mm_list, &vma->vm->active_list);
 }
@@ -2070,10 +2070,10 @@ void i915_vma_move_to_active(struct i915_vma *vma,
 static void
 i915_gem_object_retire__write(struct drm_i915_gem_object *obj)
 {
-	RQ_BUG_ON(obj->last_write_req == NULL);
-	RQ_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write_req->engine)));
+	RQ_BUG_ON(obj->last_write.request == NULL);
+	RQ_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write.request->engine)));
 
-	i915_gem_request_assign(&obj->last_write_req, NULL);
+	i915_gem_request_assign(&obj->last_write.request, NULL);
 	intel_fb_obj_flush(obj, true, ORIGIN_CS);
 }
 
@@ -2082,13 +2082,13 @@ i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int ring)
 {
 	struct i915_vma *vma;
 
-	RQ_BUG_ON(obj->last_read_req[ring] == NULL);
+	RQ_BUG_ON(obj->last_read[ring].request == NULL);
 	RQ_BUG_ON(!(obj->active & (1 << ring)));
 
 	list_del_init(&obj->ring_list[ring]);
-	i915_gem_request_assign(&obj->last_read_req[ring], NULL);
+	i915_gem_request_assign(&obj->last_read[ring].request, NULL);
 
-	if (obj->last_write_req && obj->last_write_req->engine->id == ring)
+	if (obj->last_write.request && obj->last_write.request->engine->id == ring)
 		i915_gem_object_retire__write(obj);
 
 	obj->active &= ~(1 << ring);
@@ -2107,7 +2107,7 @@ i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int ring)
 			list_move_tail(&vma->mm_list, &vma->vm->inactive_list);
 	}
 
-	i915_gem_request_assign(&obj->last_fenced_req, NULL);
+	i915_gem_request_assign(&obj->last_fence.request, NULL);
 	drm_gem_object_unreference(&obj->base);
 }
 
@@ -2334,7 +2334,7 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *ring)
 				      struct drm_i915_gem_object,
 				      ring_list[ring->id]);
 
-		if (!list_empty(&obj->last_read_req[ring->id]->list))
+		if (!list_empty(&obj->last_read[ring->id].request->list))
 			break;
 
 		i915_gem_object_retire__read(obj, ring->id);
@@ -2437,7 +2437,7 @@ i915_gem_object_flush_active(struct drm_i915_gem_object *obj)
 	for (i = 0; i < I915_NUM_RINGS; i++) {
 		struct drm_i915_gem_request *req;
 
-		req = obj->last_read_req[i];
+		req = obj->last_read[i].request;
 		if (req == NULL)
 			continue;
 
@@ -2517,10 +2517,10 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 	drm_gem_object_unreference(&obj->base);
 
 	for (i = 0; i < I915_NUM_RINGS; i++) {
-		if (obj->last_read_req[i] == NULL)
+		if (obj->last_read[i].request == NULL)
 			continue;
 
-		req[n++] = i915_gem_request_reference(obj->last_read_req[i]);
+		req[n++] = i915_gem_request_reference(obj->last_read[i].request);
 	}
 
 	mutex_unlock(&dev->struct_mutex);
@@ -2611,12 +2611,12 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj,
 
 	n = 0;
 	if (readonly) {
-		if (obj->last_write_req)
-			req[n++] = obj->last_write_req;
+		if (obj->last_write.request)
+			req[n++] = obj->last_write.request;
 	} else {
 		for (i = 0; i < I915_NUM_RINGS; i++)
-			if (obj->last_read_req[i])
-				req[n++] = obj->last_read_req[i];
+			if (obj->last_read[i].request)
+				req[n++] = obj->last_read[i].request;
 	}
 	for (i = 0; i < n; i++) {
 		ret = __i915_gem_object_sync(obj, to, req[i]);
@@ -3688,8 +3688,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
 
 	BUILD_BUG_ON(I915_NUM_RINGS > 16);
 	args->busy = obj->active << 16;
-	if (obj->last_write_req)
-		args->busy |= obj->last_write_req->engine->id;
+	if (obj->last_write.request)
+		args->busy |= obj->last_write.request->engine->id;
 
 unref:
 	drm_gem_object_unreference(&obj->base);
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 9b5f63f118bb..667b9b1e8700 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1085,7 +1085,7 @@ i915_gem_execbuffer_move_to_active(struct list_head *vmas,
 
 		i915_vma_move_to_active(vma, req);
 		if (obj->base.write_domain) {
-			i915_gem_request_assign(&obj->last_write_req, req);
+			i915_gem_request_mark_active(req, &obj->last_write);
 
 			intel_fb_obj_invalidate(obj, ORIGIN_CS);
 
@@ -1093,7 +1093,7 @@ i915_gem_execbuffer_move_to_active(struct list_head *vmas,
 			obj->base.write_domain &= ~I915_GEM_GPU_DOMAINS;
 		}
 		if (entry->flags & EXEC_OBJECT_NEEDS_FENCE) {
-			i915_gem_request_assign(&obj->last_fenced_req, req);
+			i915_gem_request_mark_active(req, &obj->last_fence);
 			if (entry->flags & __EXEC_OBJECT_HAS_FENCE) {
 				struct drm_i915_private *dev_priv = req->i915;
 				list_move_tail(&dev_priv->fence_regs[obj->fence_reg].lru_list,
diff --git a/drivers/gpu/drm/i915/i915_gem_fence.c b/drivers/gpu/drm/i915/i915_gem_fence.c
index 598198543dcd..ab29c237ffa9 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence.c
@@ -261,12 +261,12 @@ 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_fenced_req) {
-		int ret = i915_wait_request(obj->last_fenced_req);
+	if (obj->last_fence.request) {
+		int ret = i915_wait_request(obj->last_fence.request);
 		if (ret)
 			return ret;
 
-		i915_gem_request_assign(&obj->last_fenced_req, NULL);
+		i915_gem_request_assign(&obj->last_fence.request, NULL);
 	}
 
 	return 0;
diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
index 83a8115d9b96..ae8eed22e294 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.h
+++ b/drivers/gpu/drm/i915/i915_gem_request.h
@@ -200,4 +200,41 @@ static inline bool i915_gem_request_completed(struct drm_i915_gem_request *req)
 				 req->fence.seqno);
 }
 
+/* We treat requests as fences. This is not be to confused with our
+ * "fence registers" but pipeline synchronisation objects ala GL_ARB_sync.
+ * We use the fences to synchronize access from the CPU with activity on the
+ * GPU, for example, we should not rewrite an object's PTE whilst the GPU
+ * is reading them. We also track fences at a higher level to provide
+ * implicit synchronisation around GEM objects, e.g. set-domain will wait
+ * for outstanding GPU rendering before marking the object ready for CPU
+ * access.
+ *
+ * In order to use a fence, the object must track the fence it needs to
+ * serialise with. For example, GEM objects want to track both read and
+ * write access so that we can perform concurrent read operations between
+ * the CPU and GPU engines, as well as waiting for all rendering to
+ * complete or waiting for the last GPU user of a "fence register". The object
+ * then embeds a @drm_i915_gem_request_active to track the most recent (in
+ * retirment order) request relevant for the desired mode of access.
+ * The @drm_i915_gem_request_active is updated with
+ * i915_gem_request_mark_active() to track the most recent fence request,
+ * typically this is done as part of i915_vma_move_to_active().
+ *
+ * When the @drm_i915_gem_request_active completes (is retired), it will
+ * signal its completion to the owner through a callback as well as mark
+ * itself as idle (drm_i915_gem_request_active.request == NULL). The owner
+ * can then perform any action, such as delayed freeing of an active
+ * resource including itself.
+ */
+struct drm_i915_gem_request_active {
+	struct drm_i915_gem_request *request;
+};
+
+static inline void
+i915_gem_request_mark_active(struct drm_i915_gem_request *request,
+			     struct drm_i915_gem_request_active *active)
+{
+	i915_gem_request_assign(&active->request, request);
+}
+
 #endif /* I915_GEM_REQUEST_H */
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index 7410f6c962e7..c7588135a82d 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_fenced_req ||
+				obj->last_fence.request ||
 				obj->fence_reg != I915_FENCE_REG_NONE;
 
 			obj->tiling_mode = args->tiling_mode;
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 9b708fa304aa..82baa370ae09 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -708,8 +708,8 @@ static void capture_bo(struct drm_i915_error_buffer *err,
 	err->size = obj->base.size;
 	err->name = obj->base.name;
 	for (i = 0; i < I915_NUM_RINGS; i++)
-		err->rseqno[i] = i915_gem_request_get_seqno(obj->last_read_req[i]);
-	err->wseqno = i915_gem_request_get_seqno(obj->last_write_req);
+		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->gtt_offset = vma->node.start;
 	err->read_domains = obj->base.read_domains;
 	err->write_domain = obj->base.write_domain;
@@ -721,7 +721,7 @@ 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->ring = obj->last_write_req ?  obj->last_write_req->engine->id : -1;
+	err->ring = obj->last_write.request ? obj->last_write.request->engine->id : -1;
 	err->cache_level = obj->cache_level;
 }
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f6ec3b5d846d..db461b120299 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11246,7 +11246,7 @@ static bool use_mmio_flip(struct intel_engine_cs *ring,
 						       false))
 		return true;
 	else
-		return ring != i915_gem_request_get_engine(obj->last_write_req);
+		return ring != i915_gem_request_get_engine(obj->last_write.request);
 }
 
 static void skl_do_mmio_flip(struct intel_crtc *intel_crtc,
@@ -11391,7 +11391,7 @@ static int intel_queue_mmio_flip(struct drm_device *dev,
 		return -ENOMEM;
 
 	mmio_flip->i915 = to_i915(dev);
-	mmio_flip->req = i915_gem_request_reference(obj->last_write_req);
+	mmio_flip->req = i915_gem_request_reference(obj->last_write.request);
 	mmio_flip->crtc = to_intel_crtc(crtc);
 	mmio_flip->rotation = crtc->primary->state->rotation;
 
@@ -11590,7 +11590,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 	} else if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev)) {
 		ring = &dev_priv->ring[BCS];
 	} else if (INTEL_INFO(dev)->gen >= 7) {
-		ring = i915_gem_request_get_engine(obj->last_write_req);
+		ring = i915_gem_request_get_engine(obj->last_write.request);
 		if (ring == NULL || ring->id != RCS)
 			ring = &dev_priv->ring[BCS];
 	} else {
@@ -11631,7 +11631,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 			goto cleanup_unpin;
 
 		i915_gem_request_assign(&work->flip_queued_req,
-					obj->last_write_req);
+					obj->last_write.request);
 	} else {
 		ret = dev_priv->display.queue_flip(dev, crtc, fb, obj, request,
 						   page_flip_flags);
@@ -13745,7 +13745,7 @@ intel_prepare_plane_fb(struct drm_plane *plane,
 				to_intel_plane_state(new_state);
 
 			i915_gem_request_assign(&plane_state->wait_req,
-						obj->last_write_req);
+						obj->last_write.request);
 		}
 
 		i915_gem_track_fb(old_obj, obj, intel_plane->frontbuffer_bit);
-- 
2.6.4

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