1 files changed, 511 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
new file mode 100644
index 000000000..762127dd5
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -0,0 +1,511 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2018 Intel Corporation
+ */
+
+#include <linux/mutex.h>
+
+#include "i915_drv.h"
+#include "i915_request.h"
+#include "i915_scheduler.h"
+
+static struct kmem_cache *slab_dependencies;
+static struct kmem_cache *slab_priorities;
+
+static DEFINE_SPINLOCK(schedule_lock);
+
+static const struct i915_request *
+node_to_request(const struct i915_sched_node *node)
+{
+	return container_of(node, const struct i915_request, sched);
+}
+
+static inline bool node_started(const struct i915_sched_node *node)
+{
+	return i915_request_started(node_to_request(node));
+}
+
+static inline bool node_signaled(const struct i915_sched_node *node)
+{
+	return i915_request_completed(node_to_request(node));
+}
+
+static inline struct i915_priolist *to_priolist(struct rb_node *rb)
+{
+	return rb_entry(rb, struct i915_priolist, node);
+}
+
+static void assert_priolists(struct i915_sched_engine * const sched_engine)
+{
+	struct rb_node *rb;
+	long last_prio;
+
+	if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
+		return;
+
+	GEM_BUG_ON(rb_first_cached(&sched_engine->queue) !=
+		   rb_first(&sched_engine->queue.rb_root));
+
+	last_prio = INT_MAX;
+	for (rb = rb_first_cached(&sched_engine->queue); rb; rb = rb_next(rb)) {
+		const struct i915_priolist *p = to_priolist(rb);
+
+		GEM_BUG_ON(p->priority > last_prio);
+		last_prio = p->priority;
+	}
+}
+
+struct list_head *
+i915_sched_lookup_priolist(struct i915_sched_engine *sched_engine, int prio)
+{
+	struct i915_priolist *p;
+	struct rb_node **parent, *rb;
+	bool first = true;
+
+	lockdep_assert_held(&sched_engine->lock);
+	assert_priolists(sched_engine);
+
+	if (unlikely(sched_engine->no_priolist))
+		prio = I915_PRIORITY_NORMAL;
+
+find_priolist:
+	/* most positive priority is scheduled first, equal priorities fifo */
+	rb = NULL;
+	parent = &sched_engine->queue.rb_root.rb_node;
+	while (*parent) {
+		rb = *parent;
+		p = to_priolist(rb);
+		if (prio > p->priority) {
+			parent = &rb->rb_left;
+		} else if (prio < p->priority) {
+			parent = &rb->rb_right;
+			first = false;
+		} else {
+			return &p->requests;
+		}
+	}
+
+	if (prio == I915_PRIORITY_NORMAL) {
+		p = &sched_engine->default_priolist;
+	} else {
+		p = kmem_cache_alloc(slab_priorities, GFP_ATOMIC);
+		/* Convert an allocation failure to a priority bump */
+		if (unlikely(!p)) {
+			prio = I915_PRIORITY_NORMAL; /* recurses just once */
+
+			/* To maintain ordering with all rendering, after an
+			 * allocation failure we have to disable all scheduling.
+			 * Requests will then be executed in fifo, and schedule
+			 * will ensure that dependencies are emitted in fifo.
+			 * There will be still some reordering with existing
+			 * requests, so if userspace lied about their
+			 * dependencies that reordering may be visible.
+			 */
+			sched_engine->no_priolist = true;
+			goto find_priolist;
+		}
+	}
+
+	p->priority = prio;
+	INIT_LIST_HEAD(&p->requests);
+
+	rb_link_node(&p->node, rb, parent);
+	rb_insert_color_cached(&p->node, &sched_engine->queue, first);
+
+	return &p->requests;
+}
+
+void __i915_priolist_free(struct i915_priolist *p)
+{
+	kmem_cache_free(slab_priorities, p);
+}
+
+struct sched_cache {
+	struct list_head *priolist;
+};
+
+static struct i915_sched_engine *
+lock_sched_engine(struct i915_sched_node *node,
+		  struct i915_sched_engine *locked,
+		  struct sched_cache *cache)
+{
+	const struct i915_request *rq = node_to_request(node);
+	struct i915_sched_engine *sched_engine;
+
+	GEM_BUG_ON(!locked);
+
+	/*
+	 * Virtual engines complicate acquiring the engine timeline lock,
+	 * as their rq->engine pointer is not stable until under that
+	 * engine lock. The simple ploy we use is to take the lock then
+	 * check that the rq still belongs to the newly locked engine.
+	 */
+	while (locked != (sched_engine = READ_ONCE(rq->engine)->sched_engine)) {
+		spin_unlock(&locked->lock);
+		memset(cache, 0, sizeof(*cache));
+		spin_lock(&sched_engine->lock);
+		locked = sched_engine;
+	}
+
+	GEM_BUG_ON(locked != sched_engine);
+	return locked;
+}
+
+static void __i915_schedule(struct i915_sched_node *node,
+			    const struct i915_sched_attr *attr)
+{
+	const int prio = max(attr->priority, node->attr.priority);
+	struct i915_sched_engine *sched_engine;
+	struct i915_dependency *dep, *p;
+	struct i915_dependency stack;
+	struct sched_cache cache;
+	LIST_HEAD(dfs);
+
+	/* Needed in order to use the temporary link inside i915_dependency */
+	lockdep_assert_held(&schedule_lock);
+	GEM_BUG_ON(prio == I915_PRIORITY_INVALID);
+
+	if (node_signaled(node))
+		return;
+
+	stack.signaler = node;
+	list_add(&stack.dfs_link, &dfs);
+
+	/*
+	 * Recursively bump all dependent priorities to match the new request.
+	 *
+	 * A naive approach would be to use recursion:
+	 * static void update_priorities(struct i915_sched_node *node, prio) {
+	 *	list_for_each_entry(dep, &node->signalers_list, signal_link)
+	 *		update_priorities(dep->signal, prio)
+	 *	queue_request(node);
+	 * }
+	 * but that may have unlimited recursion depth and so runs a very
+	 * real risk of overunning the kernel stack. Instead, we build
+	 * a flat list of all dependencies starting with the current request.
+	 * As we walk the list of dependencies, we add all of its dependencies
+	 * to the end of the list (this may include an already visited
+	 * request) and continue to walk onwards onto the new dependencies. The
+	 * end result is a topological list of requests in reverse order, the
+	 * last element in the list is the request we must execute first.
+	 */
+	list_for_each_entry(dep, &dfs, dfs_link) {
+		struct i915_sched_node *node = dep->signaler;
+
+		/* If we are already flying, we know we have no signalers */
+		if (node_started(node))
+			continue;
+
+		/*
+		 * Within an engine, there can be no cycle, but we may
+		 * refer to the same dependency chain multiple times
+		 * (redundant dependencies are not eliminated) and across
+		 * engines.
+		 */
+		list_for_each_entry(p, &node->signalers_list, signal_link) {
+			GEM_BUG_ON(p == dep); /* no cycles! */
+
+			if (node_signaled(p->signaler))
+				continue;
+
+			if (prio > READ_ONCE(p->signaler->attr.priority))
+				list_move_tail(&p->dfs_link, &dfs);
+		}
+	}
+
+	/*
+	 * If we didn't need to bump any existing priorities, and we haven't
+	 * yet submitted this request (i.e. there is no potential race with
+	 * execlists_submit_request()), we can set our own priority and skip
+	 * acquiring the engine locks.
+	 */
+	if (node->attr.priority == I915_PRIORITY_INVALID) {
+		GEM_BUG_ON(!list_empty(&node->link));
+		node->attr = *attr;
+
+		if (stack.dfs_link.next == stack.dfs_link.prev)
+			return;
+
+		__list_del_entry(&stack.dfs_link);
+	}
+
+	memset(&cache, 0, sizeof(cache));
+	sched_engine = node_to_request(node)->engine->sched_engine;
+	spin_lock(&sched_engine->lock);
+
+	/* Fifo and depth-first replacement ensure our deps execute before us */
+	sched_engine = lock_sched_engine(node, sched_engine, &cache);
+	list_for_each_entry_safe_reverse(dep, p, &dfs, dfs_link) {
+		struct i915_request *from = container_of(dep->signaler,
+							 struct i915_request,
+							 sched);
+		INIT_LIST_HEAD(&dep->dfs_link);
+
+		node = dep->signaler;
+		sched_engine = lock_sched_engine(node, sched_engine, &cache);
+		lockdep_assert_held(&sched_engine->lock);
+
+		/* Recheck after acquiring the engine->timeline.lock */
+		if (prio <= node->attr.priority || node_signaled(node))
+			continue;
+
+		GEM_BUG_ON(node_to_request(node)->engine->sched_engine !=
+			   sched_engine);
+
+		/* Must be called before changing the nodes priority */
+		if (sched_engine->bump_inflight_request_prio)
+			sched_engine->bump_inflight_request_prio(from, prio);
+
+		WRITE_ONCE(node->attr.priority, prio);
+
+		/*
+		 * Once the request is ready, it will be placed into the
+		 * priority lists and then onto the HW runlist. Before the
+		 * request is ready, it does not contribute to our preemption
+		 * decisions and we can safely ignore it, as it will, and
+		 * any preemption required, be dealt with upon submission.
+		 * See engine->submit_request()
+		 */
+		if (list_empty(&node->link))
+			continue;
+
+		if (i915_request_in_priority_queue(node_to_request(node))) {
+			if (!cache.priolist)
+				cache.priolist =
+					i915_sched_lookup_priolist(sched_engine,
+								   prio);
+			list_move_tail(&node->link, cache.priolist);
+		}
+
+		/* Defer (tasklet) submission until after all of our updates. */
+		if (sched_engine->kick_backend)
+			sched_engine->kick_backend(node_to_request(node), prio);
+	}
+
+	spin_unlock(&sched_engine->lock);
+}
+
+void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
+{
+	spin_lock_irq(&schedule_lock);
+	__i915_schedule(&rq->sched, attr);
+	spin_unlock_irq(&schedule_lock);
+}
+
+void i915_sched_node_init(struct i915_sched_node *node)
+{
+	INIT_LIST_HEAD(&node->signalers_list);
+	INIT_LIST_HEAD(&node->waiters_list);
+	INIT_LIST_HEAD(&node->link);
+
+	i915_sched_node_reinit(node);
+}
+
+void i915_sched_node_reinit(struct i915_sched_node *node)
+{
+	node->attr.priority = I915_PRIORITY_INVALID;
+	node->semaphores = 0;
+	node->flags = 0;
+
+	GEM_BUG_ON(!list_empty(&node->signalers_list));
+	GEM_BUG_ON(!list_empty(&node->waiters_list));
+	GEM_BUG_ON(!list_empty(&node->link));
+}
+
+static struct i915_dependency *
+i915_dependency_alloc(void)
+{
+	return kmem_cache_alloc(slab_dependencies, GFP_KERNEL);
+}
+
+static void
+i915_dependency_free(struct i915_dependency *dep)
+{
+	kmem_cache_free(slab_dependencies, dep);
+}
+
+bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
+				      struct i915_sched_node *signal,
+				      struct i915_dependency *dep,
+				      unsigned long flags)
+{
+	bool ret = false;
+
+	spin_lock_irq(&schedule_lock);
+
+	if (!node_signaled(signal)) {
+		INIT_LIST_HEAD(&dep->dfs_link);
+		dep->signaler = signal;
+		dep->waiter = node;
+		dep->flags = flags;
+
+		/* All set, now publish. Beware the lockless walkers. */
+		list_add_rcu(&dep->signal_link, &node->signalers_list);
+		list_add_rcu(&dep->wait_link, &signal->waiters_list);
+
+		/* Propagate the chains */
+		node->flags |= signal->flags;
+		ret = true;
+	}
+
+	spin_unlock_irq(&schedule_lock);
+
+	return ret;
+}
+
+int i915_sched_node_add_dependency(struct i915_sched_node *node,
+				   struct i915_sched_node *signal,
+				   unsigned long flags)
+{
+	struct i915_dependency *dep;
+
+	dep = i915_dependency_alloc();
+	if (!dep)
+		return -ENOMEM;
+
+	if (!__i915_sched_node_add_dependency(node, signal, dep,
+					      flags | I915_DEPENDENCY_ALLOC))
+		i915_dependency_free(dep);
+
+	return 0;
+}
+
+void i915_sched_node_fini(struct i915_sched_node *node)
+{
+	struct i915_dependency *dep, *tmp;
+
+	spin_lock_irq(&schedule_lock);
+
+	/*
+	 * Everyone we depended upon (the fences we wait to be signaled)
+	 * should retire before us and remove themselves from our list.
+	 * However, retirement is run independently on each timeline and
+	 * so we may be called out-of-order.
+	 */
+	list_for_each_entry_safe(dep, tmp, &node->signalers_list, signal_link) {
+		GEM_BUG_ON(!list_empty(&dep->dfs_link));
+
+		list_del_rcu(&dep->wait_link);
+		if (dep->flags & I915_DEPENDENCY_ALLOC)
+			i915_dependency_free(dep);
+	}
+	INIT_LIST_HEAD(&node->signalers_list);
+
+	/* Remove ourselves from everyone who depends upon us */
+	list_for_each_entry_safe(dep, tmp, &node->waiters_list, wait_link) {
+		GEM_BUG_ON(dep->signaler != node);
+		GEM_BUG_ON(!list_empty(&dep->dfs_link));
+
+		list_del_rcu(&dep->signal_link);
+		if (dep->flags & I915_DEPENDENCY_ALLOC)
+			i915_dependency_free(dep);
+	}
+	INIT_LIST_HEAD(&node->waiters_list);
+
+	spin_unlock_irq(&schedule_lock);
+}
+
+void i915_request_show_with_schedule(struct drm_printer *m,
+				     const struct i915_request *rq,
+				     const char *prefix,
+				     int indent)
+{
+	struct i915_dependency *dep;
+
+	i915_request_show(m, rq, prefix, indent);
+	if (i915_request_completed(rq))
+		return;
+
+	rcu_read_lock();
+	for_each_signaler(dep, rq) {
+		const struct i915_request *signaler =
+			node_to_request(dep->signaler);
+
+		/* Dependencies along the same timeline are expected. */
+		if (signaler->timeline == rq->timeline)
+			continue;
+
+		if (__i915_request_is_complete(signaler))
+			continue;
+
+		i915_request_show(m, signaler, prefix, indent + 2);
+	}
+	rcu_read_unlock();
+}
+
+static void default_destroy(struct kref *kref)
+{
+	struct i915_sched_engine *sched_engine =
+		container_of(kref, typeof(*sched_engine), ref);
+
+	tasklet_kill(&sched_engine->tasklet); /* flush the callback */
+	kfree(sched_engine);
+}
+
+static bool default_disabled(struct i915_sched_engine *sched_engine)
+{
+	return false;
+}
+
+struct i915_sched_engine *
+i915_sched_engine_create(unsigned int subclass)
+{
+	struct i915_sched_engine *sched_engine;
+
+	sched_engine = kzalloc(sizeof(*sched_engine), GFP_KERNEL);
+	if (!sched_engine)
+		return NULL;
+
+	kref_init(&sched_engine->ref);
+
+	sched_engine->queue = RB_ROOT_CACHED;
+	sched_engine->queue_priority_hint = INT_MIN;
+	sched_engine->destroy = default_destroy;
+	sched_engine->disabled = default_disabled;
+
+	INIT_LIST_HEAD(&sched_engine->requests);
+	INIT_LIST_HEAD(&sched_engine->hold);
+
+	spin_lock_init(&sched_engine->lock);
+	lockdep_set_subclass(&sched_engine->lock, subclass);
+
+	/*
+	 * Due to an interesting quirk in lockdep's internal debug tracking,
+	 * after setting a subclass we must ensure the lock is used. Otherwise,
+	 * nr_unused_locks is incremented once too often.
+	 */
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	local_irq_disable();
+	lock_map_acquire(&sched_engine->lock.dep_map);
+	lock_map_release(&sched_engine->lock.dep_map);
+	local_irq_enable();
+#endif
+
+	return sched_engine;
+}
+
+void i915_scheduler_module_exit(void)
+{
+	kmem_cache_destroy(slab_dependencies);
+	kmem_cache_destroy(slab_priorities);
+}
+
+int __init i915_scheduler_module_init(void)
+{
+	slab_dependencies = KMEM_CACHE(i915_dependency,
+					      SLAB_HWCACHE_ALIGN |
+					      SLAB_TYPESAFE_BY_RCU);
+	if (!slab_dependencies)
+		return -ENOMEM;
+
+	slab_priorities = KMEM_CACHE(i915_priolist, 0);
+	if (!slab_priorities)
+		goto err_priorities;
+
+	return 0;
+
+err_priorities:
+	kmem_cache_destroy(slab_priorities);
+	return -ENOMEM;
+}