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Commit b3dfbdf2 authored by Gustavo Padovan's avatar Gustavo Padovan Committed by Daniel Vetter
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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: default avatarGustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
Reviewed-by: default avatarGustavo Padovan <gustavo.padovan@collabora.co.uk>
Acked-by: default avatarSumit Semwal <sumit.semwal@linaro.org>
[danvet: Improve commit message as suggested by Gustavo.]
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1464786612-5010-3-git-send-email-deathsimple@vodafone.de
parent 76bf0db5

drivers/dma-buf/Makefile

+1 −1
Original line number Original line Diff line number Diff line 
obj-y := dma-buf.o fence.o reservation.o seqno-fence.o

obj-y := dma-buf.o fence.o reservation.o seqno-fence.o fence-array.o

obj-$(CONFIG_SYNC_FILE)		+= sync_file.o
 
obj-$(CONFIG_SYNC_FILE)		+= sync_file.o

drivers/dma-buf/fence-array.c

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+127 −0
Original line number Original line Diff line number Diff line 
/*

 * fence-array: aggregate fences 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.

 */



#include <linux/export.h>

#include <linux/slab.h>

#include <linux/fence-array.h>



static void fence_array_cb_func(struct fence *f, struct fence_cb *cb);



static const char *fence_array_get_driver_name(struct fence *fence)

{

	return "fence_array";

}



static const char *fence_array_get_timeline_name(struct fence *fence)

{

	return "unbound";

}



static void fence_array_cb_func(struct fence *f, struct fence_cb *cb)

{

	struct fence_array_cb *array_cb =

		container_of(cb, struct fence_array_cb, cb);

	struct fence_array *array = array_cb->array;



	if (atomic_dec_and_test(&array->num_pending))

		fence_signal(&array->base);

}



static bool fence_array_enable_signaling(struct fence *fence)

{

	struct fence_array *array = to_fence_array(fence);

	struct fence_array_cb *cb = (void *)(&array[1]);

	unsigned i;



	for (i = 0; i < array->num_fences; ++i) {

		cb[i].array = array;

		if (fence_add_callback(array->fences[i], &cb[i].cb,

				       fence_array_cb_func))

			if (atomic_dec_and_test(&array->num_pending))

				return false;

	}



	return true;

}



static bool fence_array_signaled(struct fence *fence)

{

	struct fence_array *array = to_fence_array(fence);



	return atomic_read(&array->num_pending) == 0;

}



static void fence_array_release(struct fence *fence)

{

	struct fence_array *array = to_fence_array(fence);

	unsigned i;



	for (i = 0; i < array->num_fences; ++i)

		fence_put(array->fences[i]);



	kfree(array->fences);

	fence_free(fence);

}



const struct fence_ops fence_array_ops = {

	.get_driver_name = fence_array_get_driver_name,

	.get_timeline_name = fence_array_get_timeline_name,

	.enable_signaling = fence_array_enable_signaling,

	.signaled = fence_array_signaled,

	.wait = fence_default_wait,

	.release = fence_array_release,

};



/**

 * fence_array_create - Create a custom fence array

 * @num_fences:	[in]	number of fences to add in the array

 * @fences:	[in]	array containing the fences

 * @context:	[in]	fence context to use

 * @seqno:	[in]	sequence number to use

 *

 * Allocate a fence_array object and initialize the base fence with fence_init().

 * In case of error it returns NULL.

 *

 * The caller should allocte the fences array with num_fences size

 * and fill it with the fences it wants to add to the object. Ownership of this

 * array is take and fence_put() is used on each fence on release.

 */

struct fence_array *fence_array_create(int num_fences, struct fence **fences,

				       u64 context, unsigned seqno)

{

	struct fence_array *array;

	size_t size = sizeof(*array);



	/* Allocate the callback structures behind the array. */

	size += num_fences * sizeof(struct fence_array_cb);

	array = kzalloc(size, GFP_KERNEL);

	if (!array)

		return NULL;



	spin_lock_init(&array->lock);

	fence_init(&array->base, &fence_array_ops, &array->lock,

		   context, seqno);



	array->num_fences = num_fences;

	atomic_set(&array->num_pending, num_fences);

	array->fences = fences;



	return array;

}

EXPORT_SYMBOL(fence_array_create);

include/linux/fence-array.h

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Original line number Original line Diff line number Diff line 
/*

 * 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 */