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-rw-r--r--drivers/dma-buf/dma-fence-chain.c265
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);