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Diffstat (limited to 'include/linux/seqno-fence.h')
| -rw-r--r-- | include/linux/seqno-fence.h | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/include/linux/seqno-fence.h b/include/linux/seqno-fence.h new file mode 100644 index 000000000..3cca2b8fa --- /dev/null +++ b/include/linux/seqno-fence.h @@ -0,0 +1,109 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * seqno-fence, using a dma-buf to synchronize fencing + * + * Copyright (C) 2012 Texas Instruments + * Copyright (C) 2012 Canonical Ltd + * Authors: + * Rob Clark <robdclark@gmail.com> + * Maarten Lankhorst <maarten.lankhorst@canonical.com> + */ + +#ifndef __LINUX_SEQNO_FENCE_H +#define __LINUX_SEQNO_FENCE_H + +#include <linux/dma-fence.h> +#include <linux/dma-buf.h> + +enum seqno_fence_condition { + SEQNO_FENCE_WAIT_GEQUAL, + SEQNO_FENCE_WAIT_NONZERO +}; + +struct seqno_fence { + struct dma_fence base; + + const struct dma_fence_ops *ops; + struct dma_buf *sync_buf; + uint32_t seqno_ofs; + enum seqno_fence_condition condition; +}; + +extern const struct dma_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 dma_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 + * @lock: pointer to spinlock to use for fence + * @sync_buf: buffer containing the memory location to signal on + * @context: the execution context this fence is a part of + * @seqno_ofs: the offset within @sync_buf + * @seqno: the sequence # to signal on + * @cond: fence wait condition + * @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 dma_fence_signal() + * before destruction. This will prevent possible issues from wraparound at + * time of issue vs time of check, since users can check dma_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, spinlock_t *lock, + struct dma_buf *sync_buf, uint32_t context, + uint32_t seqno_ofs, uint32_t seqno, + enum seqno_fence_condition cond, + const struct dma_fence_ops *ops) +{ + BUG_ON(!fence || !sync_buf || !ops); + BUG_ON(!ops->wait || !ops->enable_signaling || + !ops->get_driver_name || !ops->get_timeline_name); + + /* + * ops is used in dma_fence_init for get_driver_name, so needs to be + * initialized first + */ + fence->ops = ops; + dma_fence_init(&fence->base, &seqno_fence_ops, lock, context, seqno); + get_dma_buf(sync_buf); + fence->sync_buf = sync_buf; + fence->seqno_ofs = seqno_ofs; + fence->condition = cond; +} + +#endif /* __LINUX_SEQNO_FENCE_H */ |