/* SPDX-License-Identifier: GPL-2.0-only */ /* * Fence mechanism for dma-buf to allow for asynchronous dma access * * Copyright (C) 2012 Canonical Ltd * Copyright (C) 2012 Texas Instruments * * Authors: * Rob Clark <[email protected]> * Maarten Lankhorst <[email protected]> */ #ifndef __LINUX_DMA_FENCE_H #define __LINUX_DMA_FENCE_H #include <linux/err.h> #include <linux/wait.h> #include <linux/list.h> #include <linux/bitops.h> #include <linux/kref.h> #include <linux/sched.h> #include <linux/printk.h> #include <linux/rcupdate.h> #include <linux/timekeeping.h> struct dma_fence; struct dma_fence_ops; struct dma_fence_cb; /** * struct dma_fence - software synchronization primitive * @refcount: refcount for this fence * @ops: dma_fence_ops associated with this fence * @rcu: used for releasing fence with kfree_rcu * @cb_list: list of all callbacks to call * @lock: spin_lock_irqsave used for locking * @context: execution context this fence belongs to, returned by * dma_fence_context_alloc() * @seqno: the sequence number of this fence inside the execution context, * can be compared to decide which fence would be signaled later. * @flags: A mask of DMA_FENCE_FLAG_* defined below * @timestamp: Timestamp when the fence was signaled. * @error: Optional, only valid if < 0, must be set before calling * dma_fence_signal, indicates that the fence has completed with an error. * * the flags member must be manipulated and read using the appropriate * atomic ops (bit_*), so taking the spinlock will not be needed most * of the time. * * DMA_FENCE_FLAG_SIGNALED_BIT - fence is already signaled * DMA_FENCE_FLAG_TIMESTAMP_BIT - timestamp recorded for fence signaling * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT - enable_signaling might have been called * DMA_FENCE_FLAG_USER_BITS - start of the unused bits, can be used by the * implementer of the fence for its own purposes. Can be used in different * ways by different fence implementers, so do not rely on this. * * Since atomic bitops are used, this is not guaranteed to be the case. * Particularly, if the bit was set, but dma_fence_signal was called right * before this bit was set, it would have been able to set the * DMA_FENCE_FLAG_SIGNALED_BIT, before enable_signaling was called. * Adding a check for DMA_FENCE_FLAG_SIGNALED_BIT after setting * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT closes this race, and makes sure that * after dma_fence_signal was called, any enable_signaling call will have either * been completed, or never called at all. */ struct dma_fence { … }; enum dma_fence_flag_bits { … }; dma_fence_func_t; /** * struct dma_fence_cb - callback for dma_fence_add_callback() * @node: used by dma_fence_add_callback() to append this struct to fence::cb_list * @func: dma_fence_func_t to call * * This struct will be initialized by dma_fence_add_callback(), additional * data can be passed along by embedding dma_fence_cb in another struct. */ struct dma_fence_cb { … }; /** * struct dma_fence_ops - operations implemented for fence * */ struct dma_fence_ops { … }; void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops, spinlock_t *lock, u64 context, u64 seqno); void dma_fence_release(struct kref *kref); void dma_fence_free(struct dma_fence *fence); void dma_fence_describe(struct dma_fence *fence, struct seq_file *seq); /** * dma_fence_put - decreases refcount of the fence * @fence: fence to reduce refcount of */ static inline void dma_fence_put(struct dma_fence *fence) { … } /** * dma_fence_get - increases refcount of the fence * @fence: fence to increase refcount of * * Returns the same fence, with refcount increased by 1. */ static inline struct dma_fence *dma_fence_get(struct dma_fence *fence) { … } /** * dma_fence_get_rcu - get a fence from a dma_resv_list with * rcu read lock * @fence: fence to increase refcount of * * Function returns NULL if no refcount could be obtained, or the fence. */ static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence) { … } /** * dma_fence_get_rcu_safe - acquire a reference to an RCU tracked fence * @fencep: pointer to fence to increase refcount of * * Function returns NULL if no refcount could be obtained, or the fence. * This function handles acquiring a reference to a fence that may be * reallocated within the RCU grace period (such as with SLAB_TYPESAFE_BY_RCU), * so long as the caller is using RCU on the pointer to the fence. * * An alternative mechanism is to employ a seqlock to protect a bunch of * fences, such as used by struct dma_resv. When using a seqlock, * the seqlock must be taken before and checked after a reference to the * fence is acquired (as shown here). * * The caller is required to hold the RCU read lock. */ static inline struct dma_fence * dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep) { … } #ifdef CONFIG_LOCKDEP bool dma_fence_begin_signalling(void); void dma_fence_end_signalling(bool cookie); void __dma_fence_might_wait(void); #else static inline bool dma_fence_begin_signalling(void) { return true; } static inline void dma_fence_end_signalling(bool cookie) {} static inline void __dma_fence_might_wait(void) {} #endif int dma_fence_signal(struct dma_fence *fence); int dma_fence_signal_locked(struct dma_fence *fence); int dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp); int dma_fence_signal_timestamp_locked(struct dma_fence *fence, ktime_t timestamp); signed long dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout); int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb, dma_fence_func_t func); bool dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb); void dma_fence_enable_sw_signaling(struct dma_fence *fence); /** * dma_fence_is_signaled_locked - Return an indication if the fence * is signaled yet. * @fence: the fence to check * * Returns true if the fence was already signaled, false if not. Since this * function doesn't enable signaling, it is not guaranteed to ever return * true if dma_fence_add_callback(), dma_fence_wait() or * dma_fence_enable_sw_signaling() haven't been called before. * * This function requires &dma_fence.lock to be held. * * See also dma_fence_is_signaled(). */ static inline bool dma_fence_is_signaled_locked(struct dma_fence *fence) { … } /** * dma_fence_is_signaled - Return an indication if the fence is signaled yet. * @fence: the fence to check * * Returns true if the fence was already signaled, false if not. Since this * function doesn't enable signaling, it is not guaranteed to ever return * true if dma_fence_add_callback(), dma_fence_wait() or * dma_fence_enable_sw_signaling() haven't been called before. * * It's recommended for seqno fences to call dma_fence_signal when the * operation is complete, it makes it possible to prevent issues from * wraparound between time of issue and time of use by checking the return * value of this function before calling hardware-specific wait instructions. * * See also dma_fence_is_signaled_locked(). */ static inline bool dma_fence_is_signaled(struct dma_fence *fence) { … } /** * __dma_fence_is_later - return if f1 is chronologically later than f2 * @f1: the first fence's seqno * @f2: the second fence's seqno from the same context * @ops: dma_fence_ops associated with the seqno * * Returns true if f1 is chronologically later than f2. Both fences must be * from the same context, since a seqno is not common across contexts. */ static inline bool __dma_fence_is_later(u64 f1, u64 f2, const struct dma_fence_ops *ops) { … } /** * dma_fence_is_later - return if f1 is chronologically later than f2 * @f1: the first fence from the same context * @f2: the second fence from the same context * * Returns true if f1 is chronologically later than f2. Both fences must be * from the same context, since a seqno is not re-used across contexts. */ static inline bool dma_fence_is_later(struct dma_fence *f1, struct dma_fence *f2) { … } /** * dma_fence_is_later_or_same - return true if f1 is later or same as f2 * @f1: the first fence from the same context * @f2: the second fence from the same context * * Returns true if f1 is chronologically later than f2 or the same fence. Both * fences must be from the same context, since a seqno is not re-used across * contexts. */ static inline bool dma_fence_is_later_or_same(struct dma_fence *f1, struct dma_fence *f2) { … } /** * dma_fence_later - return the chronologically later fence * @f1: the first fence from the same context * @f2: the second fence from the same context * * Returns NULL if both fences are signaled, otherwise the fence that would be * signaled last. Both fences must be from the same context, since a seqno is * not re-used across contexts. */ static inline struct dma_fence *dma_fence_later(struct dma_fence *f1, struct dma_fence *f2) { … } /** * dma_fence_get_status_locked - returns the status upon completion * @fence: the dma_fence to query * * Drivers can supply an optional error status condition before they signal * the fence (to indicate whether the fence was completed due to an error * rather than success). The value of the status condition is only valid * if the fence has been signaled, dma_fence_get_status_locked() first checks * the signal state before reporting the error status. * * Returns 0 if the fence has not yet been signaled, 1 if the fence has * been signaled without an error condition, or a negative error code * if the fence has been completed in err. */ static inline int dma_fence_get_status_locked(struct dma_fence *fence) { … } int dma_fence_get_status(struct dma_fence *fence); /** * dma_fence_set_error - flag an error condition on the fence * @fence: the dma_fence * @error: the error to store * * Drivers can supply an optional error status condition before they signal * the fence, to indicate that the fence was completed due to an error * rather than success. This must be set before signaling (so that the value * is visible before any waiters on the signal callback are woken). This * helper exists to help catching erroneous setting of #dma_fence.error. */ static inline void dma_fence_set_error(struct dma_fence *fence, int error) { … } /** * dma_fence_timestamp - helper to get the completion timestamp of a fence * @fence: fence to get the timestamp from. * * After a fence is signaled the timestamp is updated with the signaling time, * but setting the timestamp can race with tasks waiting for the signaling. This * helper busy waits for the correct timestamp to appear. */ static inline ktime_t dma_fence_timestamp(struct dma_fence *fence) { … } signed long dma_fence_wait_timeout(struct dma_fence *, bool intr, signed long timeout); signed long dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count, bool intr, signed long timeout, uint32_t *idx); /** * dma_fence_wait - sleep until the fence gets signaled * @fence: the fence to wait on * @intr: if true, do an interruptible wait * * This function will return -ERESTARTSYS if interrupted by a signal, * or 0 if the fence was signaled. Other error values may be * returned on custom implementations. * * Performs a synchronous wait on this fence. It is assumed the caller * directly or indirectly holds a reference to the fence, otherwise the * fence might be freed before return, resulting in undefined behavior. * * See also dma_fence_wait_timeout() and dma_fence_wait_any_timeout(). */ static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr) { … } void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline); struct dma_fence *dma_fence_get_stub(void); struct dma_fence *dma_fence_allocate_private_stub(ktime_t timestamp); u64 dma_fence_context_alloc(unsigned num); extern const struct dma_fence_ops dma_fence_array_ops; extern const struct dma_fence_ops dma_fence_chain_ops; /** * dma_fence_is_array - check if a fence is from the array subclass * @fence: the fence to test * * Return true if it is a dma_fence_array and false otherwise. */ static inline bool dma_fence_is_array(struct dma_fence *fence) { … } /** * dma_fence_is_chain - check if a fence is from the chain subclass * @fence: the fence to test * * Return true if it is a dma_fence_chain and false otherwise. */ static inline bool dma_fence_is_chain(struct dma_fence *fence) { … } /** * dma_fence_is_container - check if a fence is a container for other fences * @fence: the fence to test * * Return true if this fence is a container for other fences, false otherwise. * This is important since we can't build up large fence structure or otherwise * we run into recursion during operation on those fences. */ static inline bool dma_fence_is_container(struct dma_fence *fence) { … } #endif /* __LINUX_DMA_FENCE_H */
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