drm/i915: Recover all available ringbuffer space following reset

Having flushed all requests from all queues, we know that all
ringbuffers must now be empty. However, since we do not reclaim
all space when retiring the request (to prevent HEADs colliding
with rapid ringbuffer wraparound) the amount of available space
on each ringbuffer upon reset is less than when we start. Do one
more pass over all the ringbuffers to reset the available space

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Arun Siluvery <arun.siluvery@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Dave Gordon <david.s.gordon@intel.com>

drivers/gpu/drm/i915/i915_gem.c

@@ -2738,6 +2738,8 @@ static void i915_gem_reset_ring_status(struct drm_i915_private *dev_priv,
 static void i915_gem_reset_ring_cleanup(struct drm_i915_private *dev_priv,
 					struct intel_engine_cs *ring)
 {
+	struct intel_ringbuffer *buffer;
+
 	while (!list_empty(&ring->active_list)) {
 		struct drm_i915_gem_object *obj;
 
@@ -2788,6 +2790,18 @@ static void i915_gem_reset_ring_cleanup(struct drm_i915_private *dev_priv,
 
 		i915_gem_request_retire(request);
 	}
+
+	/* Having flushed all requests from all queues, we know that all
+	 * ringbuffers must now be empty. However, since we do not reclaim
+	 * all space when retiring the request (to prevent HEADs colliding
+	 * with rapid ringbuffer wraparound) the amount of available space
+	 * upon reset is less than when we start. Do one more pass over
+	 * all the ringbuffers to reset last_retired_head.
+	 */
+	list_for_each_entry(buffer, &ring->buffers, link) {
+		buffer->last_retired_head = buffer->tail;
+		intel_ring_update_space(buffer);
+	}
 }
 
 void i915_gem_reset(struct drm_device *dev)

drivers/gpu/drm/i915/intel_lrc.c

@@ -1897,6 +1897,7 @@ static int logical_ring_init(struct drm_device *dev, struct intel_engine_cs *rin
 	i915_gem_batch_pool_init(dev, &ring->batch_pool);
 	init_waitqueue_head(&ring->irq_queue);
 
+	INIT_LIST_HEAD(&ring->buffers);
 	INIT_LIST_HEAD(&ring->execlist_queue);
 	INIT_LIST_HEAD(&ring->execlist_retired_req_list);
 	spin_lock_init(&ring->execlist_lock);

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -2102,10 +2102,14 @@ intel_engine_create_ringbuffer(struct intel_engine_cs *engine, int size)
 	int ret;
 
 	ring = kzalloc(sizeof(*ring), GFP_KERNEL);
-	if (ring == NULL)
+	if (ring == NULL) {
+		DRM_DEBUG_DRIVER("Failed to allocate ringbuffer %s\n",
+				 engine->name);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	ring->ring = engine;
+	list_add(&ring->link, &engine->buffers);
 
 	ring->size = size;
 	/* Workaround an erratum on the i830 which causes a hang if
@@ -2121,8 +2125,9 @@ intel_engine_create_ringbuffer(struct intel_engine_cs *engine, int size)
 
 	ret = intel_alloc_ringbuffer_obj(engine->dev, ring);
 	if (ret) {
-		DRM_ERROR("Failed to allocate ringbuffer %s: %d\n",
-			  engine->name, ret);
+		DRM_DEBUG_DRIVER("Failed to allocate ringbuffer %s: %d\n",
+				 engine->name, ret);
+		list_del(&ring->link);
 		kfree(ring);
 		return ERR_PTR(ret);
 	}
@@ -2134,6 +2139,7 @@ void
 intel_ringbuffer_free(struct intel_ringbuffer *ring)
 {
 	intel_destroy_ringbuffer_obj(ring);
+	list_del(&ring->link);
 	kfree(ring);
 }
 
@@ -2149,6 +2155,7 @@ static int intel_init_ring_buffer(struct drm_device *dev,
 	INIT_LIST_HEAD(&ring->active_list);
 	INIT_LIST_HEAD(&ring->request_list);
 	INIT_LIST_HEAD(&ring->execlist_queue);
+	INIT_LIST_HEAD(&ring->buffers);
 	i915_gem_batch_pool_init(dev, &ring->batch_pool);
 	memset(ring->semaphore.sync_seqno, 0, sizeof(ring->semaphore.sync_seqno));
 

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -100,6 +100,7 @@ struct intel_ringbuffer {
 	void __iomem *virtual_start;
 
 	struct intel_engine_cs *ring;
+	struct list_head link;
 
 	u32 head;
 	u32 tail;
@@ -157,6 +158,7 @@ struct  intel_engine_cs {
 	u32		mmio_base;
 	struct		drm_device *dev;
 	struct intel_ringbuffer *buffer;
+	struct list_head buffers;
 
 	/*
 	 * A pool of objects to use as shadow copies of client batch buffers