[PATCH 17/20] drm/i915: Move context initialisation to first-use

[Chris Wilson]

Instead of allocating a new request when allocating a context, use the
request that initiated the allocation to emit the context
initialisation. This serves two purposes, it makes the initialisation
atomic with first use (simplifying scheduling and our own error
handling). Secondly, it enables us to remove the explicit context
allocation required by higher levels of GEM and make that property of
execlists opaque (in the next patch). There is also a minor step
forwards towards convergence of legacy/execlist contexts.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h  |  1 +
 drivers/gpu/drm/i915/intel_lrc.c | 39 ++++++++++++++++++---------------------
 2 files changed, 19 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index c71220f52bc7..c0a6fbff4678 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -868,6 +868,7 @@ struct intel_context {
 		struct i915_vma *lrc_vma;
 		u64 lrc_desc;
 		uint32_t *lrc_reg_state;
+		bool initialised;
 	} engine[I915_NUM_ENGINES];
 
 	struct list_head link;
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 838abd4b42a3..d765267153c5 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -672,9 +672,10 @@ static int execlists_move_to_gpu(struct drm_i915_gem_request *req,
 
 int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request)
 {
-	int ret = 0;
+	struct intel_engine_cs *engine = request->engine;
+	int ret;
 
-	request->ringbuf = request->ctx->engine[request->engine->id].ringbuf;
+	request->ringbuf = request->ctx->engine[engine->id].ringbuf;
 
 	if (i915.enable_guc_submission) {
 		/*
@@ -689,7 +690,20 @@ int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request
 			return ret;
 	}
 
-	return intel_lr_context_pin(request->ctx, request->engine);
+	ret = intel_lr_context_pin(request->ctx, engine);
+	if (ret)
+		return ret;
+
+	if (!request->ctx->engine[engine->id].initialised) {
+		ret = engine->init_context(request);
+		if (ret) {
+			intel_lr_context_unpin(request->ctx, engine);
+			return ret;
+		}
+		request->ctx->engine[engine->id].initialised = true;
+	}
+
+	return 0;
 }
 
 static int logical_ring_wait_for_space(struct drm_i915_gem_request *req,
@@ -2634,25 +2648,8 @@ int intel_lr_context_deferred_alloc(struct intel_context *ctx,
 
 	ctx->engine[engine->id].ringbuf = ringbuf;
 	ctx->engine[engine->id].state = ctx_obj;
+	ctx->engine[engine->id].initialised = engine->init_context == NULL;
 
-	if (ctx != ctx->i915->kernel_context && engine->init_context) {
-		struct drm_i915_gem_request *req;
-
-		req = i915_gem_request_alloc(engine, ctx);
-		if (IS_ERR(req)) {
-			ret = PTR_ERR(req);
-			DRM_ERROR("ring create req: %d\n", ret);
-			goto error_ringbuf;
-		}
-
-		ret = engine->init_context(req);
-		i915_add_request_no_flush(req);
-		if (ret) {
-			DRM_ERROR("ring init context: %d\n",
-				ret);
-			goto error_ringbuf;
-		}
-	}
 	return 0;
 
 error_ringbuf:
-- 
2.8.1