dma-buf: Rename struct fence to dma_fence

I plan to usurp the short name of struct fence for a core kernel struct,
and so I need to rename the specialised fence/timeline for DMA
operations to make room.

A consensus was reached in
https://lists.freedesktop.org/archives/dri-devel/2016-July/113083.html
that making clear this fence applies to DMA operations was a good thing.
Since then the patch has grown a bit as usage increases, so hopefully it
remains a good thing!

(v2...: rebase, rerun spatch)
v3: Compile on msm, spotted a manual fixup that I broke.
v4: Try again for msm, sorry Daniel

coccinelle script:
@@

@@
- struct fence
+ struct dma_fence
@@

@@
- struct fence_ops
+ struct dma_fence_ops
@@

@@
- struct fence_cb
+ struct dma_fence_cb
@@

@@
- struct fence_array
+ struct dma_fence_array
@@

@@
- enum fence_flag_bits
+ enum dma_fence_flag_bits
@@

@@
(
- fence_init
+ dma_fence_init
|
- fence_release
+ dma_fence_release
|
- fence_free
+ dma_fence_free
|
- fence_get
+ dma_fence_get
|
- fence_get_rcu
+ dma_fence_get_rcu
|
- fence_put
+ dma_fence_put
|
- fence_signal
+ dma_fence_signal
|
- fence_signal_locked
+ dma_fence_signal_locked
|
- fence_default_wait
+ dma_fence_default_wait
|
- fence_add_callback
+ dma_fence_add_callback
|
- fence_remove_callback
+ dma_fence_remove_callback
|
- fence_enable_sw_signaling
+ dma_fence_enable_sw_signaling
|
- fence_is_signaled_locked
+ dma_fence_is_signaled_locked
|
- fence_is_signaled
+ dma_fence_is_signaled
|
- fence_is_later
+ dma_fence_is_later
|
- fence_later
+ dma_fence_later
|
- fence_wait_timeout
+ dma_fence_wait_timeout
|
- fence_wait_any_timeout
+ dma_fence_wait_any_timeout
|
- fence_wait
+ dma_fence_wait
|
- fence_context_alloc
+ dma_fence_context_alloc
|
- fence_array_create
+ dma_fence_array_create
|
- to_fence_array
+ to_dma_fence_array
|
- fence_is_array
+ dma_fence_is_array
|
- trace_fence_emit
+ trace_dma_fence_emit
|
- FENCE_TRACE
+ DMA_FENCE_TRACE
|
- FENCE_WARN
+ DMA_FENCE_WARN
|
- FENCE_ERR
+ DMA_FENCE_ERR
)
 (
 ...
 )

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161025120045.28839-1-chris@chris-wilson.co.uk

1 files changed, 437 insertions, 0 deletions

diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
new file mode 100644
index 000000000000..ba60c043a5d3
--- /dev/null
+++ b/include/linux/dma-fence.h
@@ -0,0 +1,437 @@
+/*
+ * 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.
+ * @status: 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_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 status;
+};
+
+enum dma_fence_flag_bits {
+	DMA_FENCE_FLAG_SIGNALED_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
+ * @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 dma_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 occurred that made it impossible to enable
+ * signaling. True indicates successful enabling.
+ *
+ * fence->status may be set in enable_signaling, but only when false is
+ * returned.
+ *
+ * Calling dma_fence_signal before enable_signaling is called allows
+ * for a tiny race window in which enable_signaling is called during,
+ * before, or after dma_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 dma_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 dma_fence_default_wait for default implementation.
+ * the dma_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 dma_fence_ops {
+	const char * (*get_driver_name)(struct dma_fence *fence);
+	const char * (*get_timeline_name)(struct dma_fence *fence);
+	bool (*enable_signaling)(struct dma_fence *fence);
+	bool (*signaled)(struct dma_fence *fence);
+	signed long (*wait)(struct dma_fence *fence,
+			    bool intr, signed long timeout);
+	void (*release)(struct dma_fence *fence);
+
+	int (*fill_driver_data)(struct dma_fence *fence, void *data, int size);
+	void (*fence_value_str)(struct dma_fence *fence, char *str, int size);
+	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:	[in]	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:	[in]	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:	[in]	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
+ * @fence:	[in]	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_DESTROY_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 || !dma_fence_get_rcu(fence))
+			return NULL;
+
+		/* 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_DESTROY_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:	[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 dma_fence_add_callback, dma_fence_wait or
+ * dma_fence_enable_sw_signaling haven't been called before.
+ *
+ * This function requires fence->lock to be held.
+ */
+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:	[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 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.
+ */
+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:	[in]	the first fence from the same context
+ * @f2:	[in]	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 (int)(f1->seqno - f2->seqno) > 0;
+}
+
+/**
+ * dma_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 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;
+}
+
+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);
+
+/**
+ * dma_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 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 */