[PATCH 14/17] drm/i915: Nonblocking request submission

[Chris Wilson]

Now that we have fences in place to drive request submission, we can
employ those to queue requests after their dependencies as opposed to
stalling in the middle of an execbuf ioctl. (However, we still choose to
spin before enabling the IRQ as that is faster - though contentious.)

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 10 +++++++---
 drivers/gpu/drm/i915/i915_gem_request.c    | 14 +++++++++++++-
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index e8aeca00512b..0c8e447ffdbb 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1136,9 +1136,13 @@ eb_await_request(struct drm_i915_gem_request *to,
 
 	trace_i915_gem_ring_sync_to(to, from);
 	if (!i915.semaphores) {
-		ret = i915_wait_request(from, true, NULL, NO_WAITBOOST);
-		if (ret)
-			return ret;
+		if (!i915_spin_request(from, TASK_INTERRUPTIBLE, 2)) {
+			ret = i915_sw_fence_await_dma_fence(&to->submit,
+							    &from->fence,
+							    GFP_KERNEL);
+			if (ret < 0)
+				return ret;
+		}
 	} else {
 		ret = to->engine->semaphore.sync_to(to, from);
 		if (ret)
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index e7802fe45268..f78434fe580a 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -346,7 +346,7 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
 		       struct i915_gem_context *ctx)
 {
 	struct drm_i915_private *dev_priv = engine->i915;
-	struct drm_i915_gem_request *req;
+	struct drm_i915_gem_request *req, *prev;
 	u32 seqno;
 	int ret;
 
@@ -442,6 +442,18 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
 	 */
 	req->head = req->ring->tail;
 
+	prev = i915_gem_active_peek(&engine->last_request,
+				    &req->i915->drm.struct_mutex);
+	if (prev) {
+		ret = i915_sw_fence_await_sw_fence(&req->submit,
+						   &prev->submit,
+						   GFP_KERNEL);
+		if (ret < 0) {
+			i915_add_request(req);
+			return ERR_PTR(ret);
+		}
+	}
+
 	return req;
 
 err_ctx:
-- 
2.9.3