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Diffstat (limited to 'include/linux/dma-fence.h')
| -rw-r--r-- | include/linux/dma-fence.h | 662 |
1 files changed, 662 insertions, 0 deletions
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h new file mode 100644 index 000000000..b79097b90 --- /dev/null +++ b/include/linux/dma-fence.h @@ -0,0 +1,662 @@ +/* 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 <robdclark@gmail.com> + * Maarten Lankhorst <maarten.lankhorst@canonical.com> + */ + +#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> + +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 { + spinlock_t *lock; + const struct dma_fence_ops *ops; + /* + * We clear the callback list on kref_put so that by the time we + * release the fence it is unused. No one should be adding to the + * cb_list that they don't themselves hold a reference for. + * + * The lifetime of the timestamp is similarly tied to both the + * rcu freelist and the cb_list. The timestamp is only set upon + * signaling while simultaneously notifying the cb_list. Ergo, we + * only use either the cb_list of timestamp. Upon destruction, + * neither are accessible, and so we can use the rcu. This means + * that the cb_list is *only* valid until the signal bit is set, + * and to read either you *must* hold a reference to the fence, + * and not just the rcu_read_lock. + * + * Listed in chronological order. + */ + union { + struct list_head cb_list; + /* @cb_list replaced by @timestamp on dma_fence_signal() */ + ktime_t timestamp; + /* @timestamp replaced by @rcu on dma_fence_release() */ + struct rcu_head rcu; + }; + u64 context; + u64 seqno; + unsigned long flags; + struct kref refcount; + int error; +}; + +enum dma_fence_flag_bits { + DMA_FENCE_FLAG_SIGNALED_BIT, + DMA_FENCE_FLAG_TIMESTAMP_BIT, + DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, + DMA_FENCE_FLAG_USER_BITS, /* must always be last member */ +}; + +typedef void (*dma_fence_func_t)(struct dma_fence *fence, + struct dma_fence_cb *cb); + +/** + * 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 list_head node; + dma_fence_func_t func; +}; + +/** + * struct dma_fence_ops - operations implemented for fence + * + */ +struct dma_fence_ops { + /** + * @use_64bit_seqno: + * + * True if this dma_fence implementation uses 64bit seqno, false + * otherwise. + */ + bool use_64bit_seqno; + + /** + * @get_driver_name: + * + * Returns the driver name. This is a callback to allow drivers to + * compute the name at runtime, without having it to store permanently + * for each fence, or build a cache of some sort. + * + * This callback is mandatory. + */ + const char * (*get_driver_name)(struct dma_fence *fence); + + /** + * @get_timeline_name: + * + * Return the name of the context this fence belongs to. This is a + * callback to allow drivers to compute the name at runtime, without + * having it to store permanently for each fence, or build a cache of + * some sort. + * + * This callback is mandatory. + */ + const char * (*get_timeline_name)(struct dma_fence *fence); + + /** + * @enable_signaling: + * + * Enable software signaling of fence. + * + * For fence implementations that have the capability for hw->hw + * signaling, they can implement this op to enable the necessary + * interrupts, or insert commands into cmdstream, etc, to avoid these + * costly operations for the common case where only hw->hw + * synchronization is required. This is called in the first + * dma_fence_wait() or dma_fence_add_callback() path to let the fence + * implementation know that there is another driver waiting on the + * signal (ie. hw->sw case). + * + * This function can be called from atomic context, but not + * from irq context, so normal spinlocks can be used. + * + * A return value of false indicates the fence already passed, + * or some failure occurred that made it impossible to enable + * signaling. True indicates successful enabling. + * + * &dma_fence.error may be set in enable_signaling, but only when false + * is returned. + * + * Since many implementations can call dma_fence_signal() even when before + * @enable_signaling has been called there's a race window, where the + * dma_fence_signal() might result in the final fence reference being + * released and its memory freed. To avoid this, implementations of this + * callback should grab their own reference using dma_fence_get(), to be + * released when the fence is signalled (through e.g. the interrupt + * handler). + * + * This callback is optional. If this callback is not present, then the + * driver must always have signaling enabled. + */ + bool (*enable_signaling)(struct dma_fence *fence); + + /** + * @signaled: + * + * Peek whether the fence is signaled, as a fastpath optimization for + * e.g. dma_fence_wait() or dma_fence_add_callback(). Note that this + * callback does not need to make any guarantees beyond that a fence + * once indicates as signalled must always return true from this + * callback. This callback may return false even if the fence has + * completed already, in this case information hasn't propogated throug + * the system yet. See also dma_fence_is_signaled(). + * + * May set &dma_fence.error if returning true. + * + * This callback is optional. + */ + bool (*signaled)(struct dma_fence *fence); + + /** + * @wait: + * + * Custom wait implementation, defaults to dma_fence_default_wait() if + * not set. + * + * Deprecated and should not be used by new implementations. Only used + * by existing implementations which need special handling for their + * hardware reset procedure. + * + * Must return -ERESTARTSYS if the wait is intr = true and the wait was + * interrupted, and remaining jiffies if fence has signaled, or 0 if wait + * timed out. Can also return other error values on custom implementations, + * which should be treated as if the fence is signaled. For example a hardware + * lockup could be reported like that. + */ + signed long (*wait)(struct dma_fence *fence, + bool intr, signed long timeout); + + /** + * @release: + * + * Called on destruction of fence to release additional resources. + * Can be called from irq context. This callback is optional. If it is + * NULL, then dma_fence_free() is instead called as the default + * implementation. + */ + void (*release)(struct dma_fence *fence); + + /** + * @fence_value_str: + * + * Callback to fill in free-form debug info specific to this fence, like + * the sequence number. + * + * This callback is optional. + */ + void (*fence_value_str)(struct dma_fence *fence, char *str, int size); + + /** + * @timeline_value_str: + * + * Fills in the current value of the timeline as a string, like the + * sequence number. Note that the specific fence passed to this function + * should not matter, drivers should only use it to look up the + * corresponding timeline structures. + */ + void (*timeline_value_str)(struct dma_fence *fence, + char *str, int size); +}; + +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) +{ + if (fence) + kref_put(&fence->refcount, dma_fence_release); +} + +/** + * 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) +{ + if (fence) + kref_get(&fence->refcount); + return 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) +{ + if (kref_get_unless_zero(&fence->refcount)) + return fence; + else + return NULL; +} + +/** + * 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) +{ + do { + struct dma_fence *fence; + + fence = rcu_dereference(*fencep); + if (!fence) + return NULL; + + if (!dma_fence_get_rcu(fence)) + continue; + + /* The atomic_inc_not_zero() inside dma_fence_get_rcu() + * provides a full memory barrier upon success (such as now). + * This is paired with the write barrier from assigning + * to the __rcu protected fence pointer so that if that + * pointer still matches the current fence, we know we + * have successfully acquire a reference to it. If it no + * longer matches, we are holding a reference to some other + * reallocated pointer. This is possible if the allocator + * is using a freelist like SLAB_TYPESAFE_BY_RCU where the + * fence remains valid for the RCU grace period, but it + * may be reallocated. When using such allocators, we are + * responsible for ensuring the reference we get is to + * the right fence, as below. + */ + if (fence == rcu_access_pointer(*fencep)) + return rcu_pointer_handoff(fence); + + dma_fence_put(fence); + } while (1); +} + +#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) +{ + if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) + return true; + + if (fence->ops->signaled && fence->ops->signaled(fence)) { + dma_fence_signal_locked(fence); + return true; + } + + return false; +} + +/** + * 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) +{ + if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) + return true; + + if (fence->ops->signaled && fence->ops->signaled(fence)) { + dma_fence_signal(fence); + return true; + } + + return false; +} + +/** + * __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) +{ + /* This is for backward compatibility with drivers which can only handle + * 32bit sequence numbers. Use a 64bit compare when the driver says to + * do so. + */ + if (ops->use_64bit_seqno) + return f1 > f2; + + return (int)(lower_32_bits(f1) - lower_32_bits(f2)) > 0; +} + +/** + * 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) +{ + if (WARN_ON(f1->context != f2->context)) + return false; + + return __dma_fence_is_later(f1->seqno, f2->seqno, f1->ops); +} + +/** + * 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) +{ + return f1 == f2 || dma_fence_is_later(f1, 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) +{ + if (WARN_ON(f1->context != f2->context)) + return NULL; + + /* + * Can't check just DMA_FENCE_FLAG_SIGNALED_BIT here, it may never + * have been set if enable_signaling wasn't called, and enabling that + * here is overkill. + */ + if (dma_fence_is_later(f1, f2)) + return dma_fence_is_signaled(f1) ? NULL : f1; + else + return dma_fence_is_signaled(f2) ? NULL : 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) +{ + if (dma_fence_is_signaled_locked(fence)) + return fence->error ?: 1; + else + return 0; +} + +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) +{ + WARN_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)); + WARN_ON(error >= 0 || error < -MAX_ERRNO); + + fence->error = 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) +{ + if (WARN_ON(!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))) + return ktime_get(); + + while (!test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags)) + cpu_relax(); + + return fence->timestamp; +} + +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) +{ + signed long ret; + + /* Since dma_fence_wait_timeout cannot timeout with + * MAX_SCHEDULE_TIMEOUT, only valid return values are + * -ERESTARTSYS and MAX_SCHEDULE_TIMEOUT. + */ + ret = dma_fence_wait_timeout(fence, intr, MAX_SCHEDULE_TIMEOUT); + + return ret < 0 ? ret : 0; +} + +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) +{ + return fence->ops == &dma_fence_array_ops; +} + +/** + * 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) +{ + return fence->ops == &dma_fence_chain_ops; +} + +/** + * 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) +{ + return dma_fence_is_array(fence) || dma_fence_is_chain(fence); +} + +#endif /* __LINUX_DMA_FENCE_H */ |