/*
* Fence mechanism for dma-buf and to allow for asynchronous dma access
*
* Copyright (C) 2012 Canonical Ltd
* Copyright (C) 2012 Texas Instruments
*
* Authors:
* Rob Clark <robdclark@gmail.com>
* Maarten Lankhorst <maarten.lankhorst@canonical.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*/
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/atomic.h>
#include <linux/fence.h>
/*
* fence context counter: each execution context should have its own
* fence context, this allows checking if fences belong to the same
* context or not. One device can have multiple separate contexts,
* and they're used if some engine can run independently of another.
*/
static atomic_t fence_context_counter = ATOMIC_INIT(0);
/**
* fence_context_alloc - allocate an array of fence contexts
* @num: [in] amount of contexts to allocate
*
* This function will return the first index of the number of fences allocated.
* The fence context is used for setting fence->context to a unique number.
*/
unsigned fence_context_alloc(unsigned num)
{
BUG_ON(!num);
return atomic_add_return(num, &fence_context_counter) - num;
}
EXPORT_SYMBOL(fence_context_alloc);
/**
* fence_signal_locked - signal completion of a fence
* @fence: the fence to signal
*
* Signal completion for software callbacks on a fence, this will unblock
* fence_wait() calls and run all the callbacks added with
* fence_add_callback(). Can be called multiple times, but since a fence
* can only go from unsignaled to signaled state, it will only be effective
* the first time.
*
* Unlike fence_signal, this function must be called with fence->lock held.
*/
int fence_signal_locked(struct fence *fence)
{
struct fence_cb *cur, *tmp;
int ret = 0;
if (WARN_ON(!fence))
return -EINVAL;
if (!ktime_to_ns(fence->timestamp)) {
fence->timestamp = ktime_get();
smp_mb__before_atomic();
}
if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
ret = -EINVAL;
/*
* we might have raced with the unlocked fence_signal,
* still run through all callbacks
*/
}
list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
list_del_init(&cur->node);
cur->func(fence, cur);
}
return ret;
}
EXPORT_SYMBOL(fence_signal_locked);
/**
* fence_signal - signal completion of a fence
* @fence: the fence to signal
*
* Signal completion for software callbacks on a fence, this will unblock
* fence_wait() calls and run all the callbacks added with
* fence_add_callback(). Can be called multiple times, but since a fence
* can only go from unsignaled to signaled state, it will only be effective
* the first time.
*/
int fence_signal(struct fence *fence)
{
unsigned long flags;
if (!fence)
return -EINVAL;
if (!ktime_to_ns(fence->timestamp)) {
fence->timestamp = ktime_get();
smp_mb__before_atomic();
}
if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
return -EINVAL;
if (test_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {
struct fence_cb *cur, *tmp;
spin_lock_irqsave(fence->lock, flags);
list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
list_del_init(&cur->node);
cur->func(fence, cur);
}
spin_unlock_irqrestore(fence->lock, flags);
}
return 0;
}
EXPORT_SYMBOL(fence_signal);
/**
* fence_wait_timeout - sleep until the fence gets signaled
* or until timeout elapses
* @fence: [in] the fence to wait on
* @intr: [in] if true, do an interruptible wait
* @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
*
* Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
* remaining timeout in jiffies on success. Other error values may be
* returned on custom implementations.
*
* Performs a synchronous wait on this fence. It is assumed the caller
* directly or indirectly (buf-mgr between reservation and committing)
* holds a reference to the fence, otherwise the fence might be
* freed before return, resulting in undefined behavior.
*/
signed long
fence_wait_timeout(struct fence *fence, bool intr, signed long timeout)
{
signed long ret;
if (WARN_ON(timeout < 0))
return -EINVAL;
if (timeout == 0)
return fence_is_signaled(fence);
ret = fence->ops->wait(fence, intr, timeout);
return ret;
}
EXPORT_SYMBOL(fence_wait_timeout);
void fence_release(struct kref *kref)
{
struct fence *fence =
container_of(kref, struct fence, refcount);
BUG_ON(!list_empty(&fence->cb_list));
if (fence->ops->release)
fence->ops->release(fence);
else
fence_free(fence);
}
EXPORT_SYMBOL(fence_release);
void fence_free(struct fence *fence)
{
kfree_rcu(fence, rcu);
}
EXPORT_SYMBOL(fence_free);
/**
* fence_enable_sw_signaling - enable signaling on fence
* @fence: [in] the fence to enable
*
* this will request for sw signaling to be enabled, to make the fence
* complete as soon as possible
*/
void fence_enable_sw_signaling(struct fence *fence)
{
unsigned long flags;
if (!test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags) &&
!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
spin_lock_irqsave(fence->lock, flags);
if (!fence->ops->enable_signaling(fence))
fence_signal_locked(fence);
spin_unlock_irqrestore(fence->lock, flags);
}
}
EXPORT_SYMBOL(fence_enable_sw_signaling);
/**
* fence_add_callback - add a callback to be called when the fence
* is signaled
* @fence: [in] the fence to wait on
* @cb: [in] the callback to register
* @func: [in] the function to call
*
* cb will be initialized by fence_add_callback, no initialization
* by the caller is required. Any number of callbacks can be registered
* to a fence, but a callback can only be registered to one fence at a time.
*
* Note that the callback can be called from an atomic context. If
* fence is already signaled, this function will return -ENOENT (and
* *not* call the callback)
*
* Add a software callback to the fence. Same restrictions apply to
* refcount as it does to fence_wait, however the caller doesn't need to
* keep a refcount to fence afterwards: when software access is enabled,
* the creator of the fence is required to keep the fence alive until
* after it signals with fence_signal. The callback itself can be called
* from irq context.
*
*/
int fence_add_callback(struct fence *fence, struct fence_cb *cb,
fence_func_t func)
{
unsigned long flags;
int ret = 0;
bool was_set;
if (WARN_ON(!fence || !func))
return -EINVAL;
if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
INIT_LIST_HEAD(&cb->node);
return -ENOENT;
}
spin_lock_irqsave(fence->lock, flags);
was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
ret = -ENOENT;
else if (!was_set) {
if (!fence->ops->enable_signaling(fence)) {
fence_signal_locked(fence);
ret = -ENOENT;
}
}
if (!ret) {
cb->func = func;
list_add_tail(&cb->node, &fence->cb_list);
} else
INIT_LIST_HEAD(&cb->node);
spin_unlock_irqrestore(fence->lock, flags);
return ret;
}
EXPORT_SYMBOL(fence_add_callback);
/**
* fence_remove_callback - remove a callback from the signaling list
* @fence: [in] the fence to wait on
* @cb: [in] the callback to remove
*
* Remove a previously queued callback from the fence. This function returns
* true if the callback is successfully removed, or false if the fence has
* already been signaled.
*
* *WARNING*:
* Cancelling a callback should only be done if you really know what you're
* doing, since deadlocks and race conditions could occur all too easily. For
* this reason, it should only ever be done on hardware lockup recovery,
* with a reference held to the fence.
*/
bool
fence_remove_callback(struct fence *fence, struct fence_cb *cb)
{
unsigned long flags;
bool ret;
spin_lock_irqsave(fence->lock, flags);
ret = !list_empty(&cb->node);
if (ret)
list_del_init(&cb->node);
spin_unlock_irqrestore(fence->lock, flags);
return ret;
}
EXPORT_SYMBOL(fence_remove_callback);
struct default_wait_cb {
struct fence_cb base;
struct task_struct *task;
};
static bool
fence_test_signaled_any(struct fence **fences, uint32_t count)
{
int i;
for (i = 0; i < count; ++i) {
struct fence *fence = fences[i];
if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
return true;
}
return false;
}
/**
* fence_wait_any_timeout - sleep until any fence gets signaled
* or until timeout elapses
* @fences: [in] array of fences to wait on
* @count: [in] number of fences to wait on
* @intr: [in] if true, do an interruptible wait
* @timeout: [in] timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
*
* Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
* interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
* on success.
*
* Synchronous waits for the first fence in the array to be signaled. The
* caller needs to hold a reference to all fences in the array, otherwise a
* fence might be freed before return, resulting in undefined behavior.
*/
/**
* fence_init - Initialize a custom fence.
* @fence: [in] the fence to initialize
* @ops: [in] the fence_ops for operations on this fence
* @lock: [in] the irqsafe spinlock to use for locking this fence
* @context: [in] the execution context this fence is run on
* @seqno: [in] a linear increasing sequence number for this context
*
* Initializes an allocated fence, the caller doesn't have to keep its
* refcount after committing with this fence, but it will need to hold a
* refcount again if fence_ops.enable_signaling gets called. This can
* be used for other implementing other types of fence.
*
* context and seqno are used for easy comparison between fences, allowing
* to check which fence is later by simply using fence_later.
*/
void
fence_init(struct fence *fence, const struct fence_ops *ops,
spinlock_t *lock, unsigned context, unsigned seqno)
{
BUG_ON(!lock);
BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||
!ops->get_driver_name || !ops->get_timeline_name);
kref_init(&fence->refcount);
fence->ops = ops;
INIT_LIST_HEAD(&fence->cb_list);
fence->lock = lock;
fence->context = context;
fence->seqno = seqno;
fence->flags = 0UL;
}
EXPORT_SYMBOL(fence_init);