On Wed, Nov 18, 2020 at 9:28 PM <veeras@xxxxxxxxxxxxxx> wrote: > > On 2020-11-12 10:27, Veera Sundaram Sankaran wrote: > > Some drivers have hardware capability to get the precise timestamp of > > certain events based on which the fences are triggered. This allows it > > to set accurate timestamp factoring out any software and IRQ latencies. > > Move the timestamp parameter out of union in dma_fence struct to allow > > signaling drivers to set it. If the parameter is not set, ktime_get is > > used to set the current time to fence timestamp during > > dma_fence_signal. > > > > @Sumit Semwal / @Gustavo Padovan, > Can you please help in reviewing this change as it falls in dma-fence > files. Please answer my question on the 2nd patch. This is new uabi behaviour, we have a bunch of requirements for this kind of work: https://dri.freedesktop.org/docs/drm/gpu/drm-uapi.html#open-source-userspace-requirements Thanks, Daniel > Thanks, > Veera > > > Signed-off-by: Veera Sundaram Sankaran <veeras@xxxxxxxxxxxxxx> > > --- > > drivers/dma-buf/dma-fence.c | 18 ++++++++++-------- > > include/linux/dma-fence.h | 15 +++------------ > > 2 files changed, 13 insertions(+), 20 deletions(-) > > > > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c > > index 43624b4..7cef49a 100644 > > --- a/drivers/dma-buf/dma-fence.c > > +++ b/drivers/dma-buf/dma-fence.c > > @@ -4,6 +4,7 @@ > > * > > * Copyright (C) 2012 Canonical Ltd > > * Copyright (C) 2012 Texas Instruments > > + * Copyright (c) 2020 The Linux Foundation. All rights reserved. > > * > > * Authors: > > * Rob Clark <robdclark@xxxxxxxxx> > > @@ -329,7 +330,6 @@ void __dma_fence_might_wait(void) > > int dma_fence_signal_locked(struct dma_fence *fence) > > { > > struct dma_fence_cb *cur, *tmp; > > - struct list_head cb_list; > > > > lockdep_assert_held(fence->lock); > > > > @@ -337,16 +337,18 @@ int dma_fence_signal_locked(struct dma_fence > > *fence) > > &fence->flags))) > > return -EINVAL; > > > > - /* Stash the cb_list before replacing it with the timestamp */ > > - list_replace(&fence->cb_list, &cb_list); > > - > > - fence->timestamp = ktime_get(); > > + /* set current time, if not set by signaling driver */ > > + if (!fence->timestamp) > > + fence->timestamp = ktime_get(); > > set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags); > > trace_dma_fence_signaled(fence); > > > > - list_for_each_entry_safe(cur, tmp, &cb_list, node) { > > - INIT_LIST_HEAD(&cur->node); > > - cur->func(fence, cur); > > + if (!list_empty(&fence->cb_list)) { > > + list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) { > > + INIT_LIST_HEAD(&cur->node); > > + cur->func(fence, cur); > > + } > > + INIT_LIST_HEAD(&fence->cb_list); > > } > > > > return 0; > > diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h > > index 09e23ad..a9eebaf 100644 > > --- a/include/linux/dma-fence.h > > +++ b/include/linux/dma-fence.h > > @@ -4,6 +4,7 @@ > > * > > * Copyright (C) 2012 Canonical Ltd > > * Copyright (C) 2012 Texas Instruments > > + * Copyright (c) 2020 The Linux Foundation. All rights reserved. > > * > > * Authors: > > * Rob Clark <robdclark@xxxxxxxxx> > > @@ -70,26 +71,16 @@ struct dma_fence { > > * release the fence it is unused. No one should be adding to the > > * cb_list that they don't themselves hold a reference for. > > * > > - * The lifetime of the timestamp is similarly tied to both the > > - * rcu freelist and the cb_list. The timestamp is only set upon > > - * signaling while simultaneously notifying the cb_list. Ergo, we > > - * only use either the cb_list of timestamp. Upon destruction, > > - * neither are accessible, and so we can use the rcu. This means > > - * that the cb_list is *only* valid until the signal bit is set, > > - * and to read either you *must* hold a reference to the fence, > > - * and not just the rcu_read_lock. > > - * > > * Listed in chronological order. > > */ > > union { > > struct list_head cb_list; > > - /* @cb_list replaced by @timestamp on dma_fence_signal() */ > > - ktime_t timestamp; > > - /* @timestamp replaced by @rcu on dma_fence_release() */ > > + /* @cb_list replaced by @rcu on dma_fence_release() */ > > struct rcu_head rcu; > > }; > > u64 context; > > u64 seqno; > > + ktime_t timestamp; > > unsigned long flags; > > struct kref refcount; > > int error; -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
