1 files changed, 360 insertions, 0 deletions

diff --git a/include/linux/fence.h b/include/linux/fence.h
new file mode 100644
index 000000000000..d174585b874b
--- /dev/null
+++ b/include/linux/fence.h
@@ -0,0 +1,360 @@
+/*
+ * 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_FENCE_H
+#define __LINUX_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 fence;
+struct fence_ops;
+struct fence_cb;
+
+/**
+ * struct fence - software synchronization primitive
+ * @refcount: refcount for this fence
+ * @ops: 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
+ *           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 FENCE_FLAG_* defined below
+ * @timestamp: Timestamp when the fence was signaled.
+ * @status: Optional, only valid if < 0, must be set before calling
+ * 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.
+ *
+ * FENCE_FLAG_SIGNALED_BIT - fence is already signaled
+ * FENCE_FLAG_ENABLE_SIGNAL_BIT - enable_signaling might have been called*
+ * 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 fence_signal was called right
+ * before this bit was set, it would have been able to set the
+ * FENCE_FLAG_SIGNALED_BIT, before enable_signaling was called.
+ * Adding a check for FENCE_FLAG_SIGNALED_BIT after setting
+ * FENCE_FLAG_ENABLE_SIGNAL_BIT closes this race, and makes sure that
+ * after fence_signal was called, any enable_signaling call will have either
+ * been completed, or never called at all.
+ */
+struct fence {
+        struct kref refcount;
+        const struct fence_ops *ops;
+        struct rcu_head rcu;
+        struct list_head cb_list;
+        spinlock_t *lock;
+        unsigned context, seqno;
+        unsigned long flags;
+        ktime_t timestamp;
+        int status;
+};
+
+enum fence_flag_bits {
+        FENCE_FLAG_SIGNALED_BIT,
+        FENCE_FLAG_ENABLE_SIGNAL_BIT,
+        FENCE_FLAG_USER_BITS, /* must always be last member */
+};
+
+typedef void (*fence_func_t)(struct fence *fence, struct fence_cb *cb);
+
+/**
+ * struct fence_cb - callback for fence_add_callback
+ * @node: used by fence_add_callback to append this struct to fence::cb_list
+ * @func: fence_func_t to call
+ *
+ * This struct will be initialized by fence_add_callback, additional
+ * data can be passed along by embedding fence_cb in another struct.
+ */
+struct fence_cb {
+        struct list_head node;
+        fence_func_t func;
+};
+
+/**
+ * struct fence_ops - operations implemented for fence
+ * @get_driver_name: returns the driver name.
+ * @get_timeline_name: return the name of the context this fence belongs to.
+ * @enable_signaling: enable software signaling of fence.
+ * @signaled: [optional] peek whether the fence is signaled, can be null.
+ * @wait: custom wait implementation, or fence_default_wait.
+ * @release: [optional] called on destruction of fence, can be null
+ * @fill_driver_data: [optional] callback to fill in free-form debug info
+ * Returns amount of bytes filled, or -errno.
+ * @fence_value_str: [optional] fills in the value of the fence as a string
+ * @timeline_value_str: [optional] fills in the current value of the timeline
+ * as a string
+ *
+ * Notes on enable_signaling:
+ * For fence implementations that have the capability for hw->hw
+ * signaling, they can implement this op to enable the necessary
+ * irqs, or insert commands into cmdstream, etc.  This is called
+ * in the first wait() or 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 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 occured that made it impossible to enable
+ * signaling. True indicates succesful enabling.
+ *
+ * fence->status may be set in enable_signaling, but only when false is
+ * returned.
+ *
+ * Calling fence_signal before enable_signaling is called allows
+ * for a tiny race window in which enable_signaling is called during,
+ * before, or after fence_signal. To fight this, it is recommended
+ * that before enable_signaling returns true an extra reference is
+ * taken on the fence, to be released when the fence is signaled.
+ * This will mean fence_signal will still be called twice, but
+ * the second time will be a noop since it was already signaled.
+ *
+ * Notes on signaled:
+ * May set fence->status if returning true.
+ *
+ * Notes on wait:
+ * Must not be NULL, set to fence_default_wait for default implementation.
+ * the fence_default_wait implementation should work for any fence, as long
+ * as enable_signaling works correctly.
+ *
+ * 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.
+ *
+ * Notes on release:
+ * Can be NULL, this function allows additional commands to run on
+ * destruction of the fence. Can be called from irq context.
+ * If pointer is set to NULL, kfree will get called instead.
+ */
+
+struct fence_ops {
+        const char * (*get_driver_name)(struct fence *fence);
+        const char * (*get_timeline_name)(struct fence *fence);
+        bool (*enable_signaling)(struct fence *fence);
+        bool (*signaled)(struct fence *fence);
+        signed long (*wait)(struct fence *fence, bool intr, signed long timeout);
+        void (*release)(struct fence *fence);
+
+        int (*fill_driver_data)(struct fence *fence, void *data, int size);
+        void (*fence_value_str)(struct fence *fence, char *str, int size);
+        void (*timeline_value_str)(struct fence *fence, char *str, int size);
+};
+
+void fence_init(struct fence *fence, const struct fence_ops *ops,
+                spinlock_t *lock, unsigned context, unsigned seqno);
+
+void fence_release(struct kref *kref);
+void fence_free(struct fence *fence);
+
+/**
+ * fence_get - increases refcount of the fence
+ * @fence:      [in]    fence to increase refcount of
+ *
+ * Returns the same fence, with refcount increased by 1.
+ */
+static inline struct fence *fence_get(struct fence *fence)
+{
+        if (fence)
+                kref_get(&fence->refcount);
+        return fence;
+}
+
+/**
+ * fence_get_rcu - get a fence from a reservation_object_list with rcu read lock
+ * @fence:      [in]    fence to increase refcount of
+ *
+ * Function returns NULL if no refcount could be obtained, or the fence.
+ */
+static inline struct fence *fence_get_rcu(struct fence *fence)
+{
+        if (kref_get_unless_zero(&fence->refcount))
+                return fence;
+        else
+                return NULL;
+}
+
+/**
+ * fence_put - decreases refcount of the fence
+ * @fence:      [in]    fence to reduce refcount of
+ */
+static inline void fence_put(struct fence *fence)
+{
+        if (fence)
+                kref_put(&fence->refcount, fence_release);
+}
+
+int fence_signal(struct fence *fence);
+int fence_signal_locked(struct fence *fence);
+signed long fence_default_wait(struct fence *fence, bool intr, signed long timeout);
+int fence_add_callback(struct fence *fence, struct fence_cb *cb,
+                       fence_func_t func);
+bool fence_remove_callback(struct fence *fence, struct fence_cb *cb);
+void fence_enable_sw_signaling(struct fence *fence);
+
+/**
+ * fence_is_signaled_locked - Return an indication if the fence is signaled yet.
+ * @fence:      [in]    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 fence_add_callback, fence_wait or fence_enable_sw_signaling
+ * haven't been called before.
+ *
+ * This function requires fence->lock to be held.
+ */
+static inline bool
+fence_is_signaled_locked(struct fence *fence)
+{
+        if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+                return true;
+
+        if (fence->ops->signaled && fence->ops->signaled(fence)) {
+                fence_signal_locked(fence);
+                return true;
+        }
+
+        return false;
+}
+
+/**
+ * fence_is_signaled - Return an indication if the fence is signaled yet.
+ * @fence:      [in]    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 fence_add_callback, fence_wait or fence_enable_sw_signaling
+ * haven't been called before.
+ *
+ * It's recommended for seqno fences to call 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.
+ */
+static inline bool
+fence_is_signaled(struct fence *fence)
+{
+        if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+                return true;
+
+        if (fence->ops->signaled && fence->ops->signaled(fence)) {
+                fence_signal(fence);
+                return true;
+        }
+
+        return false;
+}
+
+/**
+ * fence_later - return the chronologically later fence
+ * @f1: [in]    the first fence from the same context
+ * @f2: [in]    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 fence *fence_later(struct fence *f1, struct fence *f2)
+{
+        if (WARN_ON(f1->context != f2->context))
+                return NULL;
+
+        /*
+         * can't check just FENCE_FLAG_SIGNALED_BIT here, it may never have been
+         * set if enable_signaling wasn't called, and enabling that here is
+         * overkill.
+         */
+        if (f2->seqno - f1->seqno <= INT_MAX)
+                return fence_is_signaled(f2) ? NULL : f2;
+        else
+                return fence_is_signaled(f1) ? NULL : f1;
+}
+
+signed long fence_wait_timeout(struct fence *, bool intr, signed long timeout);
+
+
+/**
+ * fence_wait - sleep until the fence gets signaled
+ * @fence:      [in]    the fence to wait on
+ * @intr:       [in]    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.
+ */
+static inline signed long fence_wait(struct fence *fence, bool intr)
+{
+        signed long ret;
+
+        /* Since fence_wait_timeout cannot timeout with
+         * MAX_SCHEDULE_TIMEOUT, only valid return values are
+         * -ERESTARTSYS and MAX_SCHEDULE_TIMEOUT.
+         */
+        ret = fence_wait_timeout(fence, intr, MAX_SCHEDULE_TIMEOUT);
+
+        return ret < 0 ? ret : 0;
+}
+
+unsigned fence_context_alloc(unsigned num);
+
+#define FENCE_TRACE(f, fmt, args...) \
+        do {                                                            \
+                struct fence *__ff = (f);                               \
+                if (config_enabled(CONFIG_FENCE_TRACE))                 \
+                        pr_info("f %u#%u: " fmt,                        \
+                                __ff->context, __ff->seqno, ##args);    \
+        } while (0)
+
+#define FENCE_WARN(f, fmt, args...) \
+        do {                                                            \
+                struct fence *__ff = (f);                               \
+                pr_warn("f %u#%u: " fmt, __ff->context, __ff->seqno,    \
+                         ##args);                                       \
+        } while (0)
+
+#define FENCE_ERR(f, fmt, args...) \
+        do {                                                            \
+                struct fence *__ff = (f);                               \
+                pr_err("f %u#%u: " fmt, __ff->context, __ff->seqno,     \
+                        ##args);                                        \
+        } while (0)
+
+#endif /* __LINUX_FENCE_H */