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