[PATCH 36/48] drm/i915: Queue the idling context switch after all other timelines

[Chris Wilson]

Before suspend, we wait for the switch to the kernel context. In order
for all the other context images to be complete upon suspend, that
switch must be the last operation by the GPU (i.e. this idling request
must not overtake any pending requests). To make this request execute last,
we make it depend on every other inflight request.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c         |  9 +++++++++
 drivers/gpu/drm/i915/i915_gem_context.c | 23 +++++++++++++++++------
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 33afd2cc8a9a..ac5fd5d5d358 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4264,6 +4264,14 @@ void __i915_gem_object_release_unless_active(struct drm_i915_gem_object *obj)
 		i915_gem_object_put(obj);
 }
 
+static void assert_kernel_context_is_current(struct drm_i915_private *dev_priv)
+{
+	struct intel_engine_cs *engine;
+
+	for_each_engine(engine, dev_priv)
+		GEM_BUG_ON(engine->last_context != dev_priv->kernel_context);
+}
+
 int i915_gem_suspend(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
@@ -4293,6 +4301,7 @@ int i915_gem_suspend(struct drm_device *dev)
 
 	i915_gem_retire_requests(dev_priv);
 
+	assert_kernel_context_is_current(dev_priv);
 	i915_gem_context_lost(dev_priv);
 	mutex_unlock(&dev->struct_mutex);
 
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 1d2ab73a8f43..449cf45d94eb 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -929,21 +929,32 @@ int i915_switch_context(struct drm_i915_gem_request *req)
 int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
 {
 	struct intel_engine_cs *engine;
+	struct i915_gem_timeline *timeline;
+
+	lockdep_assert_held(&dev_priv->drm.struct_mutex);
 
 	for_each_engine(engine, dev_priv) {
 		struct drm_i915_gem_request *req;
 		int ret;
 
-		if (engine->last_context == NULL)
-			continue;
-
-		if (engine->last_context == dev_priv->kernel_context)
-			continue;
-
 		req = i915_gem_request_alloc(engine, dev_priv->kernel_context);
 		if (IS_ERR(req))
 			return PTR_ERR(req);
 
+		/* Queue this switch after all other activity */
+		list_for_each_entry(timeline, &dev_priv->gt.timelines, link) {
+			struct drm_i915_gem_request *prev;
+			struct intel_timeline *tl;
+
+			tl = &timeline->engine[engine->id];
+			prev = i915_gem_active_raw(&tl->last_request,
+						   &dev_priv->drm.struct_mutex);
+			if (prev)
+				i915_sw_fence_await_sw_fence_gfp(&req->submit,
+								 &prev->submit,
+								 GFP_KERNEL);
+		}
+
 		ret = i915_switch_context(req);
 		i915_add_request_no_flush(req);
 		if (ret)
-- 
2.9.3