[Intel-gfx] [PATCH] drm/i915: Asynchronously initialise the GPU state

[Chris Wilson]

Dave Gordon made the good suggestion that once the ringbuffers were
setup, the actual queuing of commands to program the initial GPU state
could be deferred. Since that initial state contains instructions for
setting up the first power context, we want to execute that as earlier
as possible, preferrably in the background to userspace. Then when
userspace does wake up, the first time it opens the device we just need
to flush the work to be sure that our commands are queued before any of
userspace's. (Hooking into the device open should mean we have to check
less often than say hooking into execbuffer.)

Suggested-by: Dave Gordon <david.s.gordon at intel.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Dave Gordon <david.s.gordon at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h |   2 +
 drivers/gpu/drm/i915/i915_gem.c | 113 +++++++++++++++++++++++++++-------------
 2 files changed, 79 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 3ea1fe8db63e..d4003dea97eb 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1938,6 +1938,8 @@ struct drm_i915_private {
 
 	bool edp_low_vswing;
 
+	struct work_struct init_hw_late;
+
 	/*
 	 * NOTE: This is the dri1/ums dungeon, don't add stuff here. Your patch
 	 * will be rejected. Instead look for a better place.
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 2f0fed1b9dd7..7efa71f8edd7 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5140,12 +5140,76 @@ cleanup_render_ring:
 	return ret;
 }
 
+static int
+i915_gem_init_hw_late(struct drm_i915_private *dev_priv)
+{
+	struct intel_engine_cs *ring;
+	int i, j;
+
+	for_each_ring(ring, dev_priv, i) {
+		struct drm_i915_gem_request *req;
+		int ret;
+
+		if (WARN_ON(!ring->default_context)) {
+			ret = -ENODEV;
+			goto err;
+		}
+
+		req = i915_gem_request_alloc(ring, ring->default_context);
+		if (IS_ERR(req)) {
+			ret = PTR_ERR(req);
+			goto err;
+		}
+
+		if (ring->id == RCS) {
+			for (j = 0; j < NUM_L3_SLICES(dev_priv); j++)
+				i915_gem_l3_remap(req, j);
+		}
+
+		ret = i915_ppgtt_init_ring(req);
+		if (ret) {
+			DRM_ERROR("PPGTT enable ring #%d failed %d\n", i, ret);
+			goto err_req;
+		}
+
+		ret = i915_gem_context_enable(req);
+		if (ret) {
+			DRM_ERROR("Context enable ring #%d failed %d\n", i, ret);
+			goto err_req;
+		}
+
+		i915_add_request_no_flush(req);
+		continue;
+
+err_req:
+		i915_gem_request_cancel(req);
+err:
+		return ret;
+	}
+
+	return 0;
+}
+
+static void
+i915_gem_init_hw_worker(struct work_struct *work)
+{
+	struct drm_i915_private *dev_priv =
+		container_of(work, typeof(*dev_priv), init_hw_late);
+	mutex_lock(&dev_priv->dev->struct_mutex);
+	if (i915_gem_init_hw_late(dev_priv)) {
+		DRM_ERROR("Failed to initialize GPU, declaring it wedged\n");
+		atomic_set_mask(I915_WEDGED,
+				&dev_priv->gpu_error.reset_counter);
+	}
+	mutex_unlock(&dev_priv->dev->struct_mutex);
+}
+
 int
 i915_gem_init_hw(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_engine_cs *ring;
-	int ret, i, j;
+	int ret, i;
 
 	if (INTEL_INFO(dev)->gen < 6 && !intel_enable_gtt())
 		return -EIO;
@@ -5198,41 +5262,10 @@ i915_gem_init_hw(struct drm_device *dev)
 	}
 
 	/* Now it is safe to go back round and do everything else: */
-	for_each_ring(ring, dev_priv, i) {
-		struct drm_i915_gem_request *req;
-
-		WARN_ON(!ring->default_context);
-
-		req = i915_gem_request_alloc(ring, ring->default_context);
-		if (IS_ERR(req)) {
-			ret = PTR_ERR(req);
-			i915_gem_cleanup_ringbuffer(dev);
-			goto out;
-		}
-
-		if (ring->id == RCS) {
-			for (j = 0; j < NUM_L3_SLICES(dev); j++)
-				i915_gem_l3_remap(req, j);
-		}
-
-		ret = i915_ppgtt_init_ring(req);
-		if (ret && ret != -EIO) {
-			DRM_ERROR("PPGTT enable ring #%d failed %d\n", i, ret);
-			i915_gem_request_cancel(req);
-			i915_gem_cleanup_ringbuffer(dev);
-			goto out;
-		}
-
-		ret = i915_gem_context_enable(req);
-		if (ret && ret != -EIO) {
-			DRM_ERROR("Context enable ring #%d failed %d\n", i, ret);
-			i915_gem_request_cancel(req);
-			i915_gem_cleanup_ringbuffer(dev);
-			goto out;
-		}
-
-		i915_add_request_no_flush(req);
-	}
+	if (dev->open_count == 0) /* uncontested with userspace, i.e. boot */
+		queue_work(dev_priv->wq, &dev_priv->init_hw_late);
+	else
+		ret = i915_gem_init_hw_late(dev_priv);
 
 out:
 	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
@@ -5379,6 +5412,7 @@ i915_gem_load(struct drm_device *dev)
 		init_ring_lists(&dev_priv->ring[i]);
 	for (i = 0; i < I915_MAX_NUM_FENCES; i++)
 		INIT_LIST_HEAD(&dev_priv->fence_regs[i].lru_list);
+	INIT_WORK(&dev_priv->init_hw_late, i915_gem_init_hw_worker);
 	INIT_DELAYED_WORK(&dev_priv->mm.retire_work,
 			  i915_gem_retire_work_handler);
 	INIT_DELAYED_WORK(&dev_priv->mm.idle_work,
@@ -5442,11 +5476,18 @@ void i915_gem_release(struct drm_device *dev, struct drm_file *file)
 
 int i915_gem_open(struct drm_device *dev, struct drm_file *file)
 {
+	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct drm_i915_file_private *file_priv;
 	int ret;
 
 	DRM_DEBUG_DRIVER("\n");
 
+	/* Flush ring initialisation before userspace can submit its own
+	 * batches, so the hardware initialisation commands are queued
+	 * first.
+	 */
+	flush_work(&dev_priv->init_hw_late);
+
 	file_priv = kzalloc(sizeof(*file_priv), GFP_KERNEL);
 	if (!file_priv)
 		return -ENOMEM;
-- 
2.1.4