v4.19.13 snapshot.
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
new file mode 100644
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--- /dev/null
+++ b/include/linux/dma-fence.h
@@ -0,0 +1,568 @@
+/*
+ * 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>
+ *
+ * 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.
+ */
+
+#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 {
+ struct kref refcount;
+ const struct dma_fence_ops *ops;
+ struct rcu_head rcu;
+ struct list_head cb_list;
+ spinlock_t *lock;
+ u64 context;
+ unsigned seqno;
+ unsigned long flags;
+ ktime_t timestamp;
+ 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 {
+ /**
+ * @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, unsigned 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 reservation_object_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 reservation_object. 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);
+}
+
+int dma_fence_signal(struct dma_fence *fence);
+int dma_fence_signal_locked(struct dma_fence *fence);
+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
+ *
+ * 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(u32 f1, u32 f2)
+{
+ return (int)(f1 - 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);
+}
+
+/**
+ * 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;
+}
+
+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#%u: " 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#%u: " 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#%u: " fmt, __ff->context, __ff->seqno, \
+ ##args); \
+ } while (0)
+
+#endif /* __LINUX_DMA_FENCE_H */