dma-buf/fence: add fence_array fences v6

struct fence_array inherits from struct fence and carries a
collection of fences that needs to be waited together.

It is useful to translate a sync_file to a fence to remove the complexity
of dealing with sync_files on DRM drivers. So even if there are many
fences in the sync_file that needs to waited for a commit to happen,
they all get added to the fence_collection and passed for DRM use as
a standard struct fence.

That means that no changes needed to any driver besides supporting fences.

To avoid fence_array's fence allocates a new timeline if needed (when
combining fences from different timelines).

v2: Comments by Daniel Vetter:
	- merge fence_collection_init() and fence_collection_add()
	- only add callbacks at ->enable_signalling()
	- remove fence_collection_put()
	- check for type on to_fence_collection()
	- adjust fence_is_later() and fence_later() to WARN_ON() if they
	are used with collection fences.

v3: - Initialize fence_cb.node at fence init.

    Comments by Chris Wilson:
	- return "unbound" on fence_collection_get_timeline_name()
	- don't stop adding callbacks if one fails
	- remove redundant !! on fence_collection_enable_signaling()
	- remove redundant () on fence_collection_signaled
	- use fence_default_wait() instead

v4 (chk): Rework, simplification and cleanup:
	- Drop FENCE_NO_CONTEXT handling, always allocate a context.
	- Rename to fence_array.
	- Return fixed driver name.
	- Register only one callback at a time.
	- Document that create function takes ownership of array.

v5 (chk): More work and fixes:
	- Avoid deadlocks by adding all callbacks at once again.
	- Stop trying to remove the callbacks.
	- Provide context and sequence number for the array fence.

v6 (chk): Fixes found during testing
	- Fix stupid typo in _enable_signaling().

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
[danvet: Improve commit message as suggested by Gustavo.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1464786612-5010-3-git-send-email-deathsimple@vodafone.de

1 files changed, 72 insertions, 0 deletions

diff --git a/include/linux/fence-array.h b/include/linux/fence-array.h
new file mode 100644
index 000000000000..593ab983129e
--- /dev/null
+++ b/include/linux/fence-array.h
@@ -0,0 +1,72 @@
+/*
+ * fence-array: aggregates fence to be waited together
+ *
+ * Copyright (C) 2016 Collabora Ltd
+ * Copyright (C) 2016 Advanced Micro Devices, Inc.
+ * Authors:
+ *	Gustavo Padovan <gustavo@padovan.org>
+ *	Christian König <christian.koenig@amd.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_ARRAY_H
+#define __LINUX_FENCE_ARRAY_H
+
+#include <linux/fence.h>
+
+/**
+ * struct fence_array_cb - callback helper for fence array
+ * @cb: fence callback structure for signaling
+ * @array: reference to the parent fence array object
+ */
+struct fence_array_cb {
+	struct fence_cb cb;
+	struct fence_array *array;
+};
+
+/**
+ * struct fence_array - fence to represent an array of fences
+ * @base: fence base class
+ * @lock: spinlock for fence handling
+ * @num_fences: number of fences in the array
+ * @num_pending: fences in the array still pending
+ * @fences: array of the fences
+ */
+struct fence_array {
+	struct fence base;
+
+	spinlock_t lock;
+	unsigned num_fences;
+	atomic_t num_pending;
+	struct fence **fences;
+};
+
+extern const struct fence_ops fence_array_ops;
+
+/**
+ * to_fence_array - cast a fence to a fence_array
+ * @fence: fence to cast to a fence_array
+ *
+ * Returns NULL if the fence is not a fence_array,
+ * or the fence_array otherwise.
+ */
+static inline struct fence_array *to_fence_array(struct fence *fence)
+{
+	if (fence->ops != &fence_array_ops)
+		return NULL;
+
+	return container_of(fence, struct fence_array, base);
+}
+
+struct fence_array *fence_array_create(int num_fences, struct fence **fences,
+				       u64 context, unsigned seqno);
+
+#endif /* __LINUX_FENCE_ARRAY_H */