| /* 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. |
| * |
| * The dma_fence_default_wait implementation should work for any fence, as long |
| * as @enable_signaling works correctly. This hook allows drivers to |
| * have an optimized version for the case where a process context is |
| * already available, e.g. if @enable_signaling for the general case |
| * needs to set up a worker thread. |
| * |
| * 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. |
| * |
| * This callback is optional. |
| */ |
| 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); |
| |
| /** |
| * 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_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; |
| } |
| |
| 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); |
| u64 dma_fence_context_alloc(unsigned num); |
| |
| #define DMA_FENCE_TRACE(f, fmt, args...) \ |
| do { \ |
| struct dma_fence *__ff = (f); \ |
| if (IS_ENABLED(CONFIG_DMA_FENCE_TRACE)) \ |
| pr_info("f %llu#%llu: " fmt, \ |
| __ff->context, __ff->seqno, ##args); \ |
| } while (0) |
| |
| #define DMA_FENCE_WARN(f, fmt, args...) \ |
| do { \ |
| struct dma_fence *__ff = (f); \ |
| pr_warn("f %llu#%llu: " fmt, __ff->context, __ff->seqno,\ |
| ##args); \ |
| } while (0) |
| |
| #define DMA_FENCE_ERR(f, fmt, args...) \ |
| do { \ |
| struct dma_fence *__ff = (f); \ |
| pr_err("f %llu#%llu: " fmt, __ff->context, __ff->seqno, \ |
| ##args); \ |
| } while (0) |
| |
| #endif /* __LINUX_DMA_FENCE_H */ |