[3/5] seqno-fence: Hardware dma-buf implementation of fencing (v3)

diff --git a/Documentation/DocBook/device-drivers.tmpl b/Documentation/DocBook/device-drivers.tmpl
index 6f53fc0..ad14396 100644
--- a/Documentation/DocBook/device-drivers.tmpl
+++ b/Documentation/DocBook/device-drivers.tmpl
@@ -128,6 +128,7 @@  X!Edrivers/base/interface.c
 !Edrivers/base/dma-buf.c
 !Edrivers/base/fence.c
 !Iinclude/linux/fence.h
+!Iinclude/linux/seqno-fence.h
 !Edrivers/base/dma-coherent.c
 !Edrivers/base/dma-mapping.c
      </sect1>
diff --git a/drivers/base/fence.c b/drivers/base/fence.c
index b90a09e..0a184b2 100644
--- a/drivers/base/fence.c
+++ b/drivers/base/fence.c
@@ -24,6 +24,7 @@ 
 #include <linux/slab.h>
 #include <linux/export.h>
 #include <linux/fence.h>
+#include <linux/seqno-fence.h>
 
 static int __fence_signal(struct fence *fence)
 {
@@ -335,3 +336,38 @@  struct fence *fence_create(void *priv)
 	return fence;
 }
 EXPORT_SYMBOL(fence_create);
+
+static bool seqno_enable_signaling(struct fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+	return seqno_fence->ops->enable_signaling(fence);
+}
+
+static bool seqno_signaled(struct fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+	return seqno_fence->ops->signaled && seqno_fence->ops->signaled(fence);
+}
+
+static void seqno_release(struct fence *fence)
+{
+	struct seqno_fence *f = to_seqno_fence(fence);
+
+	if (f->ops->release)
+		f->ops->release(fence);
+	dma_buf_put(f->sync_buf);
+}
+
+static long seqno_wait(struct fence *fence, bool intr, signed long timeout)
+{
+	struct seqno_fence *f = to_seqno_fence(fence);
+	return f->ops->wait(fence, intr, timeout);
+}
+
+const struct fence_ops seqno_fence_ops = {
+	.enable_signaling = seqno_enable_signaling,
+	.signaled = seqno_signaled,
+	.wait = seqno_wait,
+	.release = seqno_release
+};
+EXPORT_SYMBOL_GPL(seqno_fence_ops);
diff --git a/include/linux/seqno-fence.h b/include/linux/seqno-fence.h
new file mode 100644
index 0000000..971cebe
--- /dev/null
+++ b/include/linux/seqno-fence.h
@@ -0,0 +1,107 @@ 
+/*
+ * seqno-fence, using a dma-buf to synchronize fencing
+ *
+ * Copyright (C) 2012 Texas Instruments
+ * Copyright (C) 2012 Canonical Ltd
+ * Authors:
+ *   Rob Clark <rob.clark@linaro.org>
+ *   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.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __SEQNO_FENCE_H__
+#define __SEQNO_FENCE_H__
+
+#include <linux/fence.h>
+#include <linux/dma-buf.h>
+
+struct seqno_fence {
+	struct fence base;
+
+	const struct fence_ops *ops;
+	struct dma_buf *sync_buf;
+	uint32_t seqno_ofs;
+	uint32_t seqno;
+};
+
+extern const struct fence_ops seqno_fence_ops;
+
+/**
+ * to_seqno_fence - cast a fence to a seqno_fence
+ * @fence: fence to cast to a seqno_fence
+ *
+ * Returns NULL if the fence is not a seqno_fence,
+ * or the seqno_fence otherwise.
+ */
+static inline struct seqno_fence *
+to_seqno_fence(struct fence *fence)
+{
+	if (fence->ops != &seqno_fence_ops)
+		return NULL;
+	return container_of(fence, struct seqno_fence, base);
+}
+
+/**
+ * seqno_fence_init - initialize a seqno fence
+ * @fence: seqno_fence to initialize
+ * @sync_buf: buffer containing the memory location to signal on
+ * @seqno_ofs: the offset within @sync_buf
+ * @seqno: the sequence # to signal on
+ * @priv: value of priv member
+ * @ops: the fence_ops for operations on this seqno fence
+ *
+ * This function initializes a struct seqno_fence with passed parameters,
+ * and takes a reference on sync_buf which is released on fence destruction.
+ *
+ * A seqno_fence is a dma_fence which can complete in software when
+ * enable_signaling is called, but it also completes when
+ * (s32)((sync_buf)[seqno_ofs] - seqno) >= 0 is true
+ *
+ * The seqno_fence will take a refcount on the sync_buf until it's
+ * destroyed, but actual lifetime of sync_buf may be longer if one of the
+ * callers take a reference to it.
+ *
+ * Certain hardware have instructions to insert this type of wait condition
+ * in the command stream, so no intervention from software would be needed.
+ * This type of fence can be destroyed before completed, however a reference
+ * on the sync_buf dma-buf can be taken. It is encouraged to re-use the same
+ * dma-buf for sync_buf, since mapping or unmapping the sync_buf to the
+ * device's vm can be expensive.
+ *
+ * It is recommended for creators of seqno_fence to call fence_signal
+ * before destruction. This will prevent possible issues from wraparound at
+ * time of issue vs time of check, since users can check fence_is_signaled
+ * before submitting instructions for the hardware to wait on the fence.
+ * However, when ops.enable_signaling is not called, it doesn't have to be
+ * done as soon as possible, just before there's any real danger of seqno
+ * wraparound.
+ */
+static inline void
+seqno_fence_init(struct seqno_fence *fence,
+			struct dma_buf *sync_buf,
+			uint32_t seqno_ofs, uint32_t seqno, void *priv,
+			const struct fence_ops *ops)
+{
+	BUG_ON(!fence || !sync_buf || !ops->enable_signaling || !ops->wait);
+
+	__fence_init(&fence->base, &seqno_fence_ops, priv);
+
+	get_dma_buf(sync_buf);
+	fence->ops = ops;
+	fence->sync_buf = sync_buf;
+	fence->seqno_ofs = seqno_ofs;
+	fence->seqno = seqno;
+}
+
+#endif /* __SEQNO_FENCE_H__ */