| Message ID | 1605205643-12746-1-git-send-email-veeras@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RESEND,1/2] dma-fence: allow signaling drivers to set fence timestamp | expand |
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. Thanks, Veera > Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org> > --- > 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@gmail.com> > @@ -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@gmail.com> > @@ -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;
On Wed, Nov 18, 2020 at 9:28 PM <veeras@codeaurora.org> 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@codeaurora.org> > > --- > > 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@gmail.com> > > @@ -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@gmail.com> > > @@ -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;
On Thu, Nov 12, 2020 at 7:27 PM Veera Sundaram Sankaran <veeras@codeaurora.org> 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. > > Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org> So with they "why?" question fully resolved, I think this is a bit too much a hack. I think much better if we pass the timestamp explicitly, in a new dma_fence_signal_timestamp variant. That means a bit more work, but I think it will handle this special case cleaner. Also means we need to wire the timestamp through the entire call stack on the drm side too. So we need a drm_send_event_locked_timestamp variant too for send_vblank_event. -Daniel > --- > 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@gmail.com> > @@ -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@gmail.com> > @@ -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; > -- > 2.7.4 >
On 2020-11-19 03:58, Daniel Vetter wrote: > On Thu, Nov 12, 2020 at 7:27 PM Veera Sundaram Sankaran > <veeras@codeaurora.org> 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. >> >> Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org> > > So with they "why?" question fully resolved, I think this is a bit too > much a hack. I think much better if we pass the timestamp explicitly, > in a new dma_fence_signal_timestamp variant. That means a bit more > work, but I think it will handle this special case cleaner. > > Also means we need to wire the timestamp through the entire call stack > on the drm side too. So we need a drm_send_event_locked_timestamp > variant too for send_vblank_event. > -Daniel > @Sumit Semwal, @Gustavo Padovan, @Steven Rostedt Can you please help in getting review for the v2 patches. I have addressed the earlier comments from Daniel Vetter. https://patchwork.kernel.org/project/dri-devel/list/?series=388881&archive=both Thanks, Veera >> --- >> 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@gmail.com> >> @@ -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@gmail.com> >> @@ -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; >> -- >> 2.7.4 >>
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@gmail.com> @@ -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@gmail.com> @@ -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;
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. Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org> --- drivers/dma-buf/dma-fence.c | 18 ++++++++++-------- include/linux/dma-fence.h | 15 +++------------ 2 files changed, 13 insertions(+), 20 deletions(-)