On Mon, Feb 17, 2014 at 10:56 AM, Maarten Lankhorst <maarten.lankhorst at canonical.com> wrote: > This type of fence can be used with hardware synchronization for simple > hardware that can block execution until the condition > (dma_buf[offset] - value) >= 0 has been met. > > A software fallback still has to be provided in case the fence is used > with a device that doesn't support this mechanism. It is useful to expose > this for graphics cards that have an op to support this. > > Some cards like i915 can export those, but don't have an option to wait, > so they need the software fallback. > > I extended the original patch by Rob Clark. > > v1: Original > v2: Renamed from bikeshed to seqno, moved into dma-fence.c since > not much was left of the file. Lots of documentation added. > v3: Use fence_ops instead of custom callbacks. Moved to own file > to avoid circular dependency between dma-buf.h and fence.h > v4: Add spinlock pointer to seqno_fence_init > > Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
Reviewed-by: Rob Clark <robdclark at gmail.com> > --- > Documentation/DocBook/device-drivers.tmpl | 1 > drivers/base/fence.c | 50 +++++++++++++ > include/linux/seqno-fence.h | 109 > +++++++++++++++++++++++++++++ > 3 files changed, 160 insertions(+) > create mode 100644 include/linux/seqno-fence.h > > diff --git a/Documentation/DocBook/device-drivers.tmpl > b/Documentation/DocBook/device-drivers.tmpl > index 7a0c9ddb4818..8c85c20942c2 100644 > --- a/Documentation/DocBook/device-drivers.tmpl > +++ b/Documentation/DocBook/device-drivers.tmpl > @@ -131,6 +131,7 @@ 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/reservation.c > !Iinclude/linux/reservation.h > !Edrivers/base/dma-coherent.c > diff --git a/drivers/base/fence.c b/drivers/base/fence.c > index 12df2bf62034..cd0937127a89 100644 > --- a/drivers/base/fence.c > +++ b/drivers/base/fence.c > @@ -25,6 +25,7 @@ > #include <linux/export.h> > #include <linux/atomic.h> > #include <linux/fence.h> > +#include <linux/seqno-fence.h> > > #define CREATE_TRACE_POINTS > #include <trace/events/fence.h> > @@ -413,3 +414,52 @@ __fence_init(struct fence *fence, const struct fence_ops > *ops, > trace_fence_init(fence); > } > EXPORT_SYMBOL(__fence_init); > + > +static const char *seqno_fence_get_driver_name(struct fence *fence) { > + struct seqno_fence *seqno_fence = to_seqno_fence(fence); > + return seqno_fence->ops->get_driver_name(fence); > +} > + > +static const char *seqno_fence_get_timeline_name(struct fence *fence) { > + struct seqno_fence *seqno_fence = to_seqno_fence(fence); > + return seqno_fence->ops->get_timeline_name(fence); > +} > + > +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); > + > + dma_buf_put(f->sync_buf); > + if (f->ops->release) > + f->ops->release(fence); > + else > + kfree(f); > +} > + > +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 = { > + .get_driver_name = seqno_fence_get_driver_name, > + .get_timeline_name = seqno_fence_get_timeline_name, > + .enable_signaling = seqno_enable_signaling, > + .signaled = seqno_signaled, > + .wait = seqno_wait, > + .release = seqno_release, > +}; > +EXPORT_SYMBOL(seqno_fence_ops); > diff --git a/include/linux/seqno-fence.h b/include/linux/seqno-fence.h > new file mode 100644 > index 000000000000..952f7909128c > --- /dev/null > +++ b/include/linux/seqno-fence.h > @@ -0,0 +1,109 @@ > +/* > + * seqno-fence, using a dma-buf to synchronize fencing > + * > + * Copyright (C) 2012 Texas Instruments > + * Copyright (C) 2012 Canonical Ltd > + * Authors: > + * Rob Clark <robdclark at gmail.com> > + * Maarten Lankhorst <maarten.lankhorst at 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 __LINUX_SEQNO_FENCE_H > +#define __LINUX_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; > +}; > + > +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 > + * @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 > + * @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, spinlock_t *lock, > + struct dma_buf *sync_buf, uint32_t context, uint32_t > seqno_ofs, > + uint32_t seqno, const struct 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 __fence_init for get_driver_name, so needs to be > + * initialized first > + */ > + fence->ops = ops; > + __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; > +} > + > +#endif /* __LINUX_SEQNO_FENCE_H */ >