1 files changed, 265 insertions, 0 deletions
diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c
new file mode 100644
index 000000000..a0d920576
--- /dev/null
+++ b/drivers/dma-buf/dma-fence-chain.c
@@ -0,0 +1,265 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * fence-chain: chain fences together in a timeline
+ *
+ * Copyright (C) 2018 Advanced Micro Devices, Inc.
+ * Authors:
+ *	Christian König <christian.koenig@amd.com>
+ */
+
+#include <linux/dma-fence-chain.h>
+
+static bool dma_fence_chain_enable_signaling(struct dma_fence *fence);
+
+/**
+ * dma_fence_chain_get_prev - use RCU to get a reference to the previous fence
+ * @chain: chain node to get the previous node from
+ *
+ * Use dma_fence_get_rcu_safe to get a reference to the previous fence of the
+ * chain node.
+ */
+static struct dma_fence *dma_fence_chain_get_prev(struct dma_fence_chain *chain)
+{
+	struct dma_fence *prev;
+
+	rcu_read_lock();
+	prev = dma_fence_get_rcu_safe(&chain->prev);
+	rcu_read_unlock();
+	return prev;
+}
+
+/**
+ * dma_fence_chain_walk - chain walking function
+ * @fence: current chain node
+ *
+ * Walk the chain to the next node. Returns the next fence or NULL if we are at
+ * the end of the chain. Garbage collects chain nodes which are already
+ * signaled.
+ */
+struct dma_fence *dma_fence_chain_walk(struct dma_fence *fence)
+{
+	struct dma_fence_chain *chain, *prev_chain;
+	struct dma_fence *prev, *replacement, *tmp;
+
+	chain = to_dma_fence_chain(fence);
+	if (!chain) {
+		dma_fence_put(fence);
+		return NULL;
+	}
+
+	while ((prev = dma_fence_chain_get_prev(chain))) {
+
+		prev_chain = to_dma_fence_chain(prev);
+		if (prev_chain) {
+			if (!dma_fence_is_signaled(prev_chain->fence))
+				break;
+
+			replacement = dma_fence_chain_get_prev(prev_chain);
+		} else {
+			if (!dma_fence_is_signaled(prev))
+				break;
+
+			replacement = NULL;
+		}
+
+		tmp = unrcu_pointer(cmpxchg(&chain->prev, RCU_INITIALIZER(prev),
+					     RCU_INITIALIZER(replacement)));
+		if (tmp == prev)
+			dma_fence_put(tmp);
+		else
+			dma_fence_put(replacement);
+		dma_fence_put(prev);
+	}
+
+	dma_fence_put(fence);
+	return prev;
+}
+EXPORT_SYMBOL(dma_fence_chain_walk);
+
+/**
+ * dma_fence_chain_find_seqno - find fence chain node by seqno
+ * @pfence: pointer to the chain node where to start
+ * @seqno: the sequence number to search for
+ *
+ * Advance the fence pointer to the chain node which will signal this sequence
+ * number. If no sequence number is provided then this is a no-op.
+ *
+ * Returns EINVAL if the fence is not a chain node or the sequence number has
+ * not yet advanced far enough.
+ */
+int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno)
+{
+	struct dma_fence_chain *chain;
+
+	if (!seqno)
+		return 0;
+
+	chain = to_dma_fence_chain(*pfence);
+	if (!chain || chain->base.seqno < seqno)
+		return -EINVAL;
+
+	dma_fence_chain_for_each(*pfence, &chain->base) {
+		if ((*pfence)->context != chain->base.context ||
+		    to_dma_fence_chain(*pfence)->prev_seqno < seqno)
+			break;
+	}
+	dma_fence_put(&chain->base);
+
+	return 0;
+}
+EXPORT_SYMBOL(dma_fence_chain_find_seqno);
+
+static const char *dma_fence_chain_get_driver_name(struct dma_fence *fence)
+{
+        return "dma_fence_chain";
+}
+
+static const char *dma_fence_chain_get_timeline_name(struct dma_fence *fence)
+{
+        return "unbound";
+}
+
+static void dma_fence_chain_irq_work(struct irq_work *work)
+{
+	struct dma_fence_chain *chain;
+
+	chain = container_of(work, typeof(*chain), work);
+
+	/* Try to rearm the callback */
+	if (!dma_fence_chain_enable_signaling(&chain->base))
+		/* Ok, we are done. No more unsignaled fences left */
+		dma_fence_signal(&chain->base);
+	dma_fence_put(&chain->base);
+}
+
+static void dma_fence_chain_cb(struct dma_fence *f, struct dma_fence_cb *cb)
+{
+	struct dma_fence_chain *chain;
+
+	chain = container_of(cb, typeof(*chain), cb);
+	init_irq_work(&chain->work, dma_fence_chain_irq_work);
+	irq_work_queue(&chain->work);
+	dma_fence_put(f);
+}
+
+static bool dma_fence_chain_enable_signaling(struct dma_fence *fence)
+{
+	struct dma_fence_chain *head = to_dma_fence_chain(fence);
+
+	dma_fence_get(&head->base);
+	dma_fence_chain_for_each(fence, &head->base) {
+		struct dma_fence *f = dma_fence_chain_contained(fence);
+
+		dma_fence_get(f);
+		if (!dma_fence_add_callback(f, &head->cb, dma_fence_chain_cb)) {
+			dma_fence_put(fence);
+			return true;
+		}
+		dma_fence_put(f);
+	}
+	dma_fence_put(&head->base);
+	return false;
+}
+
+static bool dma_fence_chain_signaled(struct dma_fence *fence)
+{
+	dma_fence_chain_for_each(fence, fence) {
+		struct dma_fence *f = dma_fence_chain_contained(fence);
+
+		if (!dma_fence_is_signaled(f)) {
+			dma_fence_put(fence);
+			return false;
+		}
+	}
+
+	return true;
+}
+
+static void dma_fence_chain_release(struct dma_fence *fence)
+{
+	struct dma_fence_chain *chain = to_dma_fence_chain(fence);
+	struct dma_fence *prev;
+
+	/* Manually unlink the chain as much as possible to avoid recursion
+	 * and potential stack overflow.
+	 */
+	while ((prev = rcu_dereference_protected(chain->prev, true))) {
+		struct dma_fence_chain *prev_chain;
+
+		if (kref_read(&prev->refcount) > 1)
+		       break;
+
+		prev_chain = to_dma_fence_chain(prev);
+		if (!prev_chain)
+			break;
+
+		/* No need for atomic operations since we hold the last
+		 * reference to prev_chain.
+		 */
+		chain->prev = prev_chain->prev;
+		RCU_INIT_POINTER(prev_chain->prev, NULL);
+		dma_fence_put(prev);
+	}
+	dma_fence_put(prev);
+
+	dma_fence_put(chain->fence);
+	dma_fence_free(fence);
+}
+
+const struct dma_fence_ops dma_fence_chain_ops = {
+	.use_64bit_seqno = true,
+	.get_driver_name = dma_fence_chain_get_driver_name,
+	.get_timeline_name = dma_fence_chain_get_timeline_name,
+	.enable_signaling = dma_fence_chain_enable_signaling,
+	.signaled = dma_fence_chain_signaled,
+	.release = dma_fence_chain_release,
+};
+EXPORT_SYMBOL(dma_fence_chain_ops);
+
+/**
+ * dma_fence_chain_init - initialize a fence chain
+ * @chain: the chain node to initialize
+ * @prev: the previous fence
+ * @fence: the current fence
+ * @seqno: the sequence number to use for the fence chain
+ *
+ * Initialize a new chain node and either start a new chain or add the node to
+ * the existing chain of the previous fence.
+ */
+void dma_fence_chain_init(struct dma_fence_chain *chain,
+			  struct dma_fence *prev,
+			  struct dma_fence *fence,
+			  uint64_t seqno)
+{
+	struct dma_fence_chain *prev_chain = to_dma_fence_chain(prev);
+	uint64_t context;
+
+	spin_lock_init(&chain->lock);
+	rcu_assign_pointer(chain->prev, prev);
+	chain->fence = fence;
+	chain->prev_seqno = 0;
+
+	/* Try to reuse the context of the previous chain node. */
+	if (prev_chain && __dma_fence_is_later(seqno, prev->seqno, prev->ops)) {
+		context = prev->context;
+		chain->prev_seqno = prev->seqno;
+	} else {
+		context = dma_fence_context_alloc(1);
+		/* Make sure that we always have a valid sequence number. */
+		if (prev_chain)
+			seqno = max(prev->seqno, seqno);
+	}
+
+	dma_fence_init(&chain->base, &dma_fence_chain_ops,
+		       &chain->lock, context, seqno);
+
+	/*
+	 * Chaining dma_fence_chain container together is only allowed through
+	 * the prev fence and not through the contained fence.
+	 *
+	 * The correct way of handling this is to flatten out the fence
+	 * structure into a dma_fence_array by the caller instead.
+	 */
+	WARN_ON(dma_fence_is_chain(fence));
+}
+EXPORT_SYMBOL(dma_fence_chain_init);