// 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 <[email protected]>
*/
#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);
}
static void dma_fence_chain_set_deadline(struct dma_fence *fence,
ktime_t deadline)
{
dma_fence_chain_for_each(fence, fence) {
struct dma_fence *f = dma_fence_chain_contained(fence);
dma_fence_set_deadline(f, deadline);
}
}
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,
.set_deadline = dma_fence_chain_set_deadline,
};
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);
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