drm/i915: Split i915_gem_timeline into individual timelines

We need to move to a more flexible timeline that doesn't assume one
fence context per engine, and so allow for a single timeline to be used
across a combination of engines. This means that preallocating a fence
context per engine is now a hindrance, and so we want to introduce the
singular timeline. From the code perspective, this has the notable
advantage of clearing up a lot of mirky semantics and some clumsy
pointer chasing.

By splitting the timeline up into a single entity rather than an array
of per-engine timelines, we can realise the goal of the previous patch
of tracking the timeline alongside the ring.

v2: Tweak wait_for_idle to stop the compiling thinking that ret may be
uninitialised.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180502163839.3248-2-chris@chris-wilson.co.uk

1 files changed, 21 insertions, 27 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 1f4987dc6616..33f8a4b3c981 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -122,7 +122,6 @@ static void i915_gem_context_free(struct i915_gem_context *ctx)
 	lockdep_assert_held(&ctx->i915->drm.struct_mutex);
 	GEM_BUG_ON(!i915_gem_context_is_closed(ctx));
 
-	i915_gem_timeline_free(ctx->timeline);
 	i915_ppgtt_put(ctx->ppgtt);
 
 	for (n = 0; n < ARRAY_SIZE(ctx->__engine); n++) {
@@ -377,18 +376,6 @@ i915_gem_create_context(struct drm_i915_private *dev_priv,
 		ctx->desc_template = default_desc_template(dev_priv, ppgtt);
 	}
 
-	if (HAS_EXECLISTS(dev_priv)) {
-		struct i915_gem_timeline *timeline;
-
-		timeline = i915_gem_timeline_create(dev_priv, ctx->name);
-		if (IS_ERR(timeline)) {
-			__destroy_hw_context(ctx, file_priv);
-			return ERR_CAST(timeline);
-		}
-
-		ctx->timeline = timeline;
-	}
-
 	trace_i915_context_create(ctx);
 
 	return ctx;
@@ -590,19 +577,29 @@ void i915_gem_context_close(struct drm_file *file)
 	idr_destroy(&file_priv->context_idr);
 }
 
-static bool engine_has_idle_kernel_context(struct intel_engine_cs *engine)
+static struct i915_request *
+last_request_on_engine(struct i915_timeline *timeline,
+		       struct intel_engine_cs *engine)
 {
-	struct i915_gem_timeline *timeline;
+	struct i915_request *rq;
 
-	list_for_each_entry(timeline, &engine->i915->gt.timelines, link) {
-		struct intel_timeline *tl;
+	if (timeline == &engine->timeline)
+		return NULL;
 
-		if (timeline == &engine->i915->gt.execution_timeline)
-			continue;
+	rq = i915_gem_active_raw(&timeline->last_request,
+				 &engine->i915->drm.struct_mutex);
+	if (rq && rq->engine == engine)
+		return rq;
+
+	return NULL;
+}
 
-		tl = &timeline->engine[engine->id];
-		if (i915_gem_active_peek(&tl->last_request,
-					 &engine->i915->drm.struct_mutex))
+static bool engine_has_idle_kernel_context(struct intel_engine_cs *engine)
+{
+	struct i915_timeline *timeline;
+
+	list_for_each_entry(timeline, &engine->i915->gt.timelines, link) {
+		if (last_request_on_engine(timeline, engine))
 			return false;
 	}
 
@@ -612,7 +609,7 @@ static bool engine_has_idle_kernel_context(struct intel_engine_cs *engine)
 int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
 {
 	struct intel_engine_cs *engine;
-	struct i915_gem_timeline *timeline;
+	struct i915_timeline *timeline;
 	enum intel_engine_id id;
 
 	lockdep_assert_held(&dev_priv->drm.struct_mutex);
@@ -632,11 +629,8 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
 		/* Queue this switch after all other activity */
 		list_for_each_entry(timeline, &dev_priv->gt.timelines, link) {
 			struct i915_request *prev;
-			struct intel_timeline *tl;
 
-			tl = &timeline->engine[engine->id];
-			prev = i915_gem_active_raw(&tl->last_request,
-						   &dev_priv->drm.struct_mutex);
+			prev = last_request_on_engine(timeline, engine);
 			if (prev)
 				i915_sw_fence_await_sw_fence_gfp(&rq->submit,
 								 &prev->submit,