drm/i915: Introduce i915_gem_active for request tracking

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.
v3: Now i915_gem_active.
v4: Now with i915_gem_active_set() for attaching to the active request.
v5: Use i915_gem_active_set() from inside the retirement handlers
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/1470293567-10811-10-git-send-email-chris@chris-wilson.co.uk

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_req[id]));
+			   i915_gem_request_get_seqno(obj->last_read[id].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" : "");
@@ -195,9 +195,8 @@ 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)",
-			   i915_gem_request_get_engine(obj->last_write_req)->name);
+	if (obj->last_write.request)
+		seq_printf(m, " (%s)", obj->last_write.request->engine->name);
 	if (obj->frontbuffer_bits)
 		seq_printf(m, " (frontbuffer: 0x%03x)", obj->frontbuffer_bits);
 }

drivers/gpu/drm/i915/i915_drv.h

@@ -2242,11 +2242,10 @@ 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_ENGINES];
-	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 i915_gem_active last_read[I915_NUM_ENGINES];
+	struct i915_gem_active last_write;
+	struct i915_gem_active last_fence;
 
 	/** Current tiling stride for the object, if it's tiled. */
 	uint32_t stride;

drivers/gpu/drm/i915/i915_gem.c

@@ -1353,23 +1353,23 @@ i915_gem_object_wait_rendering(struct drm_i915_gem_object *obj,
 	int ret, i;
 
 	if (readonly) {
-		if (obj->last_write_req != NULL) {
-			ret = i915_wait_request(obj->last_write_req);
+		if (obj->last_write.request) {
+			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_ENGINES; i++) {
-			if (obj->last_read_req[i] == NULL)
+			if (!obj->last_read[i].request)
 				continue;
 
-			ret = i915_wait_request(obj->last_read_req[i]);
+			ret = i915_wait_request(obj->last_read[i].request);
 			if (ret)
 				return ret;
 
@@ -1397,9 +1397,9 @@ i915_gem_object_retire_request(struct drm_i915_gem_object *obj,
 {
 	int idx = req->engine->id;
 
-	if (obj->last_read_req[idx] == req)
+	if (obj->last_read[idx].request == req)
 		i915_gem_object_retire__read(obj, idx);
-	else if (obj->last_write_req == req)
+	else if (obj->last_write.request == req)
 		i915_gem_object_retire__write(obj);
 
 	if (!i915_reset_in_progress(&req->i915->gpu_error))
@@ -1428,7 +1428,7 @@ 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;
 
@@ -1437,7 +1437,7 @@ i915_gem_object_wait_rendering__nonblocking(struct drm_i915_gem_object *obj,
 		for (i = 0; i < I915_NUM_ENGINES; i++) {
 			struct drm_i915_gem_request *req;
 
-			req = obj->last_read_req[i];
+			req = obj->last_read[i].request;
 			if (req == NULL)
 				continue;
 
@@ -2375,7 +2375,7 @@ void i915_vma_move_to_active(struct i915_vma *vma,
 	obj->active |= intel_engine_flag(engine);
 
 	list_move_tail(&obj->engine_list[engine->id], &engine->active_list);
-	i915_gem_request_assign(&obj->last_read_req[engine->id], req);
+	i915_gem_active_set(&obj->last_read[engine->id], req);
 
 	list_move_tail(&vma->vm_link, &vma->vm->active_list);
 }
@@ -2383,10 +2383,10 @@ 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_req == NULL);
-	GEM_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write_req->engine)));
+	GEM_BUG_ON(!obj->last_write.request);
+	GEM_BUG_ON(!(obj->active & intel_engine_flag(obj->last_write.request->engine)));
 
-	i915_gem_request_assign(&obj->last_write_req, NULL);
+	i915_gem_active_set(&obj->last_write, NULL);
 	intel_fb_obj_flush(obj, true, ORIGIN_CS);
 }
 
@@ -2395,13 +2395,13 @@ i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int idx)
 {
 	struct i915_vma *vma;
 
-	GEM_BUG_ON(obj->last_read_req[idx] == NULL);
+	GEM_BUG_ON(!obj->last_read[idx].request);
 	GEM_BUG_ON(!(obj->active & (1 << idx)));
 
 	list_del_init(&obj->engine_list[idx]);
-	i915_gem_request_assign(&obj->last_read_req[idx], NULL);
+	i915_gem_active_set(&obj->last_read[idx], NULL);
 
-	if (obj->last_write_req && obj->last_write_req->engine->id == idx)
+	if (obj->last_write.request && obj->last_write.request->engine->id == idx)
 		i915_gem_object_retire__write(obj);
 
 	obj->active &= ~(1 << idx);
@@ -2420,7 +2420,7 @@ i915_gem_object_retire__read(struct drm_i915_gem_object *obj, int idx)
 			list_move_tail(&vma->vm_link, &vma->vm->inactive_list);
 	}
 
-	i915_gem_request_assign(&obj->last_fenced_req, NULL);
+	i915_gem_active_set(&obj->last_fence, NULL);
 	i915_gem_object_put(obj);
 }
 
@@ -2621,7 +2621,7 @@ 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_req[engine->id]->list))
+		if (!list_empty(&obj->last_read[engine->id].request->list))
 			break;
 
 		i915_gem_object_retire__read(obj, engine->id);
@@ -2754,7 +2754,7 @@ 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_req[i];
+		req = obj->last_read[i].request;
 		if (req == NULL)
 			continue;
 
@@ -2830,10 +2830,10 @@ 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_req[i] == NULL)
+		if (!obj->last_read[i].request)
 			continue;
 
-		req[n++] = i915_gem_request_get(obj->last_read_req[i]);
+		req[n++] = i915_gem_request_get(obj->last_read[i].request);
 	}
 
 	mutex_unlock(&dev->struct_mutex);
@@ -2924,12 +2924,12 @@ 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_ENGINES; 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]);
@@ -4026,12 +4026,12 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
 		for (i = 0; i < I915_NUM_ENGINES; i++) {
 			struct drm_i915_gem_request *req;
 
-			req = obj->last_read_req[i];
+			req = obj->last_read[i].request;
 			if (req)
 				args->busy |= 1 << (16 + req->engine->exec_id);
 		}
-		if (obj->last_write_req)
-			args->busy |= obj->last_write_req->engine->exec_id;
+		if (obj->last_write.request)
+			args->busy |= obj->last_write.request->engine->exec_id;
 	}
 
 unref:

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -1150,7 +1150,7 @@ 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_active_set(&obj->last_write, req);
 
 			intel_fb_obj_invalidate(obj, ORIGIN_CS);
 
@@ -1158,7 +1158,7 @@ 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_active_set(&obj->last_fence, req);
 			if (entry->flags & __EXEC_OBJECT_HAS_FENCE) {
 				struct drm_i915_private *dev_priv = engine->i915;
 				list_move_tail(&dev_priv->fence_regs[obj->fence_reg].lru_list,

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_active_set(&obj->last_fence, NULL);
 	}
 
 	return 0;

drivers/gpu/drm/i915/i915_gem_request.h

@@ -249,4 +249,45 @@ static inline bool i915_spin_request(const struct drm_i915_gem_request *request,
 		__i915_spin_request(request, state, timeout_us));
 }
 
+/* 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, or a pageflip will wait until the GPU is complete before showing
+ * the frame on the scanout.
+ *
+ * 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 #i915_gem_active to track the most recent (in
+ * retirement order) request relevant for the desired mode of access.
+ * The #i915_gem_active is updated with i915_gem_active_set() to track the
+ * most recent fence request, typically this is done as part of
+ * i915_vma_move_to_active().
+ *
+ * When the #i915_gem_active completes (is retired), it will
+ * signal its completion to the owner through a callback as well as mark
+ * itself as idle (i915_gem_active.request == NULL). The owner
+ * can then perform any action, such as delayed freeing of an active
+ * resource including itself.
+ */
+struct i915_gem_active {
+	struct drm_i915_gem_request *request;
+};
+
+static inline void
+i915_gem_active_set(struct i915_gem_active *active,
+		    struct drm_i915_gem_request *request)
+{
+	i915_gem_request_assign(&active->request, request);
+}
+
+#define for_each_active(mask, idx) \
+	for (; mask ? idx = ffs(mask) - 1, 1 : 0; mask &= ~BIT(idx))
+
 #endif /* I915_GEM_REQUEST_H */

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;

drivers/gpu/drm/i915/i915_gem_userptr.c

@@ -74,7 +74,7 @@ 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_req[i];
+		req = obj->last_read[i].request;
 		if (req == NULL)
 			continue;
 

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -751,8 +751,8 @@ 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_ENGINES; 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;
@@ -764,8 +764,7 @@ 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->engine = obj->last_write_req ?
-		i915_gem_request_get_engine(obj->last_write_req)->id : -1;
+	err->engine = obj->last_write.request ? obj->last_write.request->engine->id : -1;
 	err->cache_level = obj->cache_level;
 }
 

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_req);
+	return engine != i915_gem_request_get_engine(obj->last_write.request);
 }
 
 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_req);
+		engine = i915_gem_request_get_engine(obj->last_write.request);
 		if (engine == NULL || engine->id != RCS)
 			engine = &dev_priv->engine[BCS];
 	} else {
@@ -11695,7 +11695,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
 		INIT_WORK(&work->mmio_work, intel_mmio_flip_work_func);
 
 		i915_gem_request_assign(&work->flip_queued_req,
-					obj->last_write_req);
+					obj->last_write.request);
 
 		schedule_work(&work->mmio_work);
 	} else {
@@ -14043,7 +14043,7 @@ 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);
 	}
 
 	return ret;