Re: [PATCH] fence: dma-buf cross-device synchronization (v13)
Op 15-08-13 14:45, Marcin Ślusarz schreef:
> 2013/8/15 Maarten Lankhorst :
>> A fence can be attached to a buffer which is being filled or consumed
>> by hw, to allow userspace to pass the buffer without waiting to another
>> device. For example, userspace can call page_flip ioctl to display the
>> next frame of graphics after kicking the GPU but while the GPU is still
>> rendering. The display device sharing the buffer with the GPU would
>> attach a callback to get notified when the GPU's rendering-complete IRQ
>> fires, to update the scan-out address of the display, without having to
>> wake up userspace.
>>
>> A driver must allocate a fence context for each execution ring that can
>> run in parallel. The function for this takes an argument with how many
>> contexts to allocate:
>> + fence_context_alloc()
>>
>> A fence is transient, one-shot deal. It is allocated and attached
>> to one or more dma-buf's. When the one that attached it is done, with
>> the pending operation, it can signal the fence:
>> + fence_signal()
>>
>> To have a rough approximation whether a fence is fired, call:
>> + fence_is_signaled()
>>
>> The dma-buf-mgr handles tracking, and waiting on, the fences associated
>> with a dma-buf.
>>
>> The one pending on the fence can add an async callback:
>> + fence_add_callback()
>>
>> The callback can optionally be cancelled with:
>> + fence_remove_callback()
>>
>> To wait synchronously, optionally with a timeout:
>> + fence_wait()
>> + fence_wait_timeout()
>>
>> A default software-only implementation is provided, which can be used
>> by drivers attaching a fence to a buffer when they have no other means
>> for hw sync. But a memory backed fence is also envisioned, because it
>> is common that GPU's can write to, or poll on some memory location for
>> synchronization. For example:
>>
>> fence = custom_get_fence(...);
>> if ((seqno_fence = to_seqno_fence(fence)) != NULL) {
>> dma_buf *fence_buf = fence->sync_buf;
>> get_dma_buf(fence_buf);
>>
>> ... tell the hw the memory location to wait ...
>> custom_wait_on(fence_buf, fence->seqno_ofs, fence->seqno);
>> } else {
>> /* fall-back to sw sync * /
>> fence_add_callback(fence, my_cb);
>> }
>>
>> On SoC platforms, if some other hw mechanism is provided for synchronizing
>> between IP blocks, it could be supported as an alternate implementation
>> with it's own fence ops in a similar way.
>>
>> enable_signaling callback is used to provide sw signaling in case a cpu
>> waiter is requested or no compatible hardware signaling could be used.
>>
>> The intention is to provide a userspace interface (presumably via eventfd)
>> later, to be used in conjunction with dma-buf's mmap support for sw access
>> to buffers (or for userspace apps that would prefer to do their own
>> synchronization).
>>
>> v1: Original
>> v2: After discussion w/ danvet and mlankhorst on #dri-devel, we decided
>> that dma-fence didn't need to care about the sw->hw signaling path
>> (it can be handled same as sw->sw case), and therefore the fence->ops
>> can be simplified and more handled in the core. So remove the signal,
>> add_callback, cancel_callback, and wait ops, and replace with a simple
>> enable_signaling() op which can be used to inform a fence supporting
>> hw->hw signaling that one or more devices which do not support hw
>> signaling are waiting (and therefore it should enable an irq or do
>> whatever is necessary in order that the CPU is notified when the
>> fence is passed).
>> v3: Fix locking fail in attach_fence() and get_fence()
>> v4: Remove tie-in w/ dma-buf.. after discussion w/ danvet and mlankorst
>> we decided that we need to be able to attach one fence to N dma-buf's,
>> so using the list_head in dma-fence struct would be problematic.
>> v5: [ Maarten Lankhorst ] Updated for dma-bikeshed-fence and dma-buf-manager.
>> v6: [ Maarten Lankhorst ] I removed dma_fence_cancel_callback and some
>> comments
>> about checking if fence fired or not. This is broken by design.
>> waitqueue_active during destruction is now fatal, since the signaller
>> should be holding a reference in enable_signalling until it signalled
>> the fence. Pass the original dma_fence_cb along, and call __remove_wait
>> in the dma_fence_callback handler, so that no cleanup needs to be
>> performed.
>> v7: [ Maarten Lankhorst ] Set cb->func and only enable sw signaling if
>> fence wasn't signaled yet, for example for hardware fences that may
>> choose to signal blindly.
>> v8: [ Maarten Lankhorst ] Tons of tiny fixes, moved __dma_fence_init to
>> header and fixed include mess. dma-fence.h now includes dma-buf.h
>> All members are now initialized, so kmalloc can be used for
>> allocating a dma-fence. More documentation added.
>> v9: Change compiler bitfields to flags, change return type of
>> enable_signaling to bool. Rework dma_fence_wait. Added
>>
Re: [PATCH] fence: dma-buf cross-device synchronization (v13)
2013/8/15 Maarten Lankhorst :
> A fence can be attached to a buffer which is being filled or consumed
> by hw, to allow userspace to pass the buffer without waiting to another
> device. For example, userspace can call page_flip ioctl to display the
> next frame of graphics after kicking the GPU but while the GPU is still
> rendering. The display device sharing the buffer with the GPU would
> attach a callback to get notified when the GPU's rendering-complete IRQ
> fires, to update the scan-out address of the display, without having to
> wake up userspace.
>
> A driver must allocate a fence context for each execution ring that can
> run in parallel. The function for this takes an argument with how many
> contexts to allocate:
> + fence_context_alloc()
>
> A fence is transient, one-shot deal. It is allocated and attached
> to one or more dma-buf's. When the one that attached it is done, with
> the pending operation, it can signal the fence:
> + fence_signal()
>
> To have a rough approximation whether a fence is fired, call:
> + fence_is_signaled()
>
> The dma-buf-mgr handles tracking, and waiting on, the fences associated
> with a dma-buf.
>
> The one pending on the fence can add an async callback:
> + fence_add_callback()
>
> The callback can optionally be cancelled with:
> + fence_remove_callback()
>
> To wait synchronously, optionally with a timeout:
> + fence_wait()
> + fence_wait_timeout()
>
> A default software-only implementation is provided, which can be used
> by drivers attaching a fence to a buffer when they have no other means
> for hw sync. But a memory backed fence is also envisioned, because it
> is common that GPU's can write to, or poll on some memory location for
> synchronization. For example:
>
> fence = custom_get_fence(...);
> if ((seqno_fence = to_seqno_fence(fence)) != NULL) {
> dma_buf *fence_buf = fence->sync_buf;
> get_dma_buf(fence_buf);
>
> ... tell the hw the memory location to wait ...
> custom_wait_on(fence_buf, fence->seqno_ofs, fence->seqno);
> } else {
> /* fall-back to sw sync * /
> fence_add_callback(fence, my_cb);
> }
>
> On SoC platforms, if some other hw mechanism is provided for synchronizing
> between IP blocks, it could be supported as an alternate implementation
> with it's own fence ops in a similar way.
>
> enable_signaling callback is used to provide sw signaling in case a cpu
> waiter is requested or no compatible hardware signaling could be used.
>
> The intention is to provide a userspace interface (presumably via eventfd)
> later, to be used in conjunction with dma-buf's mmap support for sw access
> to buffers (or for userspace apps that would prefer to do their own
> synchronization).
>
> v1: Original
> v2: After discussion w/ danvet and mlankhorst on #dri-devel, we decided
> that dma-fence didn't need to care about the sw->hw signaling path
> (it can be handled same as sw->sw case), and therefore the fence->ops
> can be simplified and more handled in the core. So remove the signal,
> add_callback, cancel_callback, and wait ops, and replace with a simple
> enable_signaling() op which can be used to inform a fence supporting
> hw->hw signaling that one or more devices which do not support hw
> signaling are waiting (and therefore it should enable an irq or do
> whatever is necessary in order that the CPU is notified when the
> fence is passed).
> v3: Fix locking fail in attach_fence() and get_fence()
> v4: Remove tie-in w/ dma-buf.. after discussion w/ danvet and mlankorst
> we decided that we need to be able to attach one fence to N dma-buf's,
> so using the list_head in dma-fence struct would be problematic.
> v5: [ Maarten Lankhorst ] Updated for dma-bikeshed-fence and dma-buf-manager.
> v6: [ Maarten Lankhorst ] I removed dma_fence_cancel_callback and some
> comments
> about checking if fence fired or not. This is broken by design.
> waitqueue_active during destruction is now fatal, since the signaller
> should be holding a reference in enable_signalling until it signalled
> the fence. Pass the original dma_fence_cb along, and call __remove_wait
> in the dma_fence_callback handler, so that no cleanup needs to be
> performed.
> v7: [ Maarten Lankhorst ] Set cb->func and only enable sw signaling if
> fence wasn't signaled yet, for example for hardware fences that may
> choose to signal blindly.
> v8: [ Maarten Lankhorst ] Tons of tiny fixes, moved __dma_fence_init to
> header and fixed include mess. dma-fence.h now includes dma-buf.h
> All members are now initialized, so kmalloc can be used for
> allocating a dma-fence. More documentation added.
> v9: Change compiler bitfields to flags, change return type of
> enable_signaling to bool. Rework dma_fence_wait. Added
> dma_fence_is_signaled and dma_fence_wait_timeout.
> s/dma// and change exports to non GPL. Added fence_is_signaled and
>
Re: [PATCH] fence: dma-buf cross-device synchronization (v13)
2013/8/15 Maarten Lankhorst maarten.lankho...@canonical.com:
A fence can be attached to a buffer which is being filled or consumed
by hw, to allow userspace to pass the buffer without waiting to another
device. For example, userspace can call page_flip ioctl to display the
next frame of graphics after kicking the GPU but while the GPU is still
rendering. The display device sharing the buffer with the GPU would
attach a callback to get notified when the GPU's rendering-complete IRQ
fires, to update the scan-out address of the display, without having to
wake up userspace.
A driver must allocate a fence context for each execution ring that can
run in parallel. The function for this takes an argument with how many
contexts to allocate:
+ fence_context_alloc()
A fence is transient, one-shot deal. It is allocated and attached
to one or more dma-buf's. When the one that attached it is done, with
the pending operation, it can signal the fence:
+ fence_signal()
To have a rough approximation whether a fence is fired, call:
+ fence_is_signaled()
The dma-buf-mgr handles tracking, and waiting on, the fences associated
with a dma-buf.
The one pending on the fence can add an async callback:
+ fence_add_callback()
The callback can optionally be cancelled with:
+ fence_remove_callback()
To wait synchronously, optionally with a timeout:
+ fence_wait()
+ fence_wait_timeout()
A default software-only implementation is provided, which can be used
by drivers attaching a fence to a buffer when they have no other means
for hw sync. But a memory backed fence is also envisioned, because it
is common that GPU's can write to, or poll on some memory location for
synchronization. For example:
fence = custom_get_fence(...);
if ((seqno_fence = to_seqno_fence(fence)) != NULL) {
dma_buf *fence_buf = fence-sync_buf;
get_dma_buf(fence_buf);
... tell the hw the memory location to wait ...
custom_wait_on(fence_buf, fence-seqno_ofs, fence-seqno);
} else {
/* fall-back to sw sync * /
fence_add_callback(fence, my_cb);
}
On SoC platforms, if some other hw mechanism is provided for synchronizing
between IP blocks, it could be supported as an alternate implementation
with it's own fence ops in a similar way.
enable_signaling callback is used to provide sw signaling in case a cpu
waiter is requested or no compatible hardware signaling could be used.
The intention is to provide a userspace interface (presumably via eventfd)
later, to be used in conjunction with dma-buf's mmap support for sw access
to buffers (or for userspace apps that would prefer to do their own
synchronization).
v1: Original
v2: After discussion w/ danvet and mlankhorst on #dri-devel, we decided
that dma-fence didn't need to care about the sw-hw signaling path
(it can be handled same as sw-sw case), and therefore the fence-ops
can be simplified and more handled in the core. So remove the signal,
add_callback, cancel_callback, and wait ops, and replace with a simple
enable_signaling() op which can be used to inform a fence supporting
hw-hw signaling that one or more devices which do not support hw
signaling are waiting (and therefore it should enable an irq or do
whatever is necessary in order that the CPU is notified when the
fence is passed).
v3: Fix locking fail in attach_fence() and get_fence()
v4: Remove tie-in w/ dma-buf.. after discussion w/ danvet and mlankorst
we decided that we need to be able to attach one fence to N dma-buf's,
so using the list_head in dma-fence struct would be problematic.
v5: [ Maarten Lankhorst ] Updated for dma-bikeshed-fence and dma-buf-manager.
v6: [ Maarten Lankhorst ] I removed dma_fence_cancel_callback and some
comments
about checking if fence fired or not. This is broken by design.
waitqueue_active during destruction is now fatal, since the signaller
should be holding a reference in enable_signalling until it signalled
the fence. Pass the original dma_fence_cb along, and call __remove_wait
in the dma_fence_callback handler, so that no cleanup needs to be
performed.
v7: [ Maarten Lankhorst ] Set cb-func and only enable sw signaling if
fence wasn't signaled yet, for example for hardware fences that may
choose to signal blindly.
v8: [ Maarten Lankhorst ] Tons of tiny fixes, moved __dma_fence_init to
header and fixed include mess. dma-fence.h now includes dma-buf.h
All members are now initialized, so kmalloc can be used for
allocating a dma-fence. More documentation added.
v9: Change compiler bitfields to flags, change return type of
enable_signaling to bool. Rework dma_fence_wait. Added
dma_fence_is_signaled and dma_fence_wait_timeout.
s/dma// and change exports to non GPL. Added fence_is_signaled and
fence_enable_sw_signaling calls, add ability to override default
wait operation.
v10:
Re: [PATCH] fence: dma-buf cross-device synchronization (v13)
Op 15-08-13 14:45, Marcin Ślusarz schreef:
2013/8/15 Maarten Lankhorst maarten.lankho...@canonical.com:
A fence can be attached to a buffer which is being filled or consumed
by hw, to allow userspace to pass the buffer without waiting to another
device. For example, userspace can call page_flip ioctl to display the
next frame of graphics after kicking the GPU but while the GPU is still
rendering. The display device sharing the buffer with the GPU would
attach a callback to get notified when the GPU's rendering-complete IRQ
fires, to update the scan-out address of the display, without having to
wake up userspace.
A driver must allocate a fence context for each execution ring that can
run in parallel. The function for this takes an argument with how many
contexts to allocate:
+ fence_context_alloc()
A fence is transient, one-shot deal. It is allocated and attached
to one or more dma-buf's. When the one that attached it is done, with
the pending operation, it can signal the fence:
+ fence_signal()
To have a rough approximation whether a fence is fired, call:
+ fence_is_signaled()
The dma-buf-mgr handles tracking, and waiting on, the fences associated
with a dma-buf.
The one pending on the fence can add an async callback:
+ fence_add_callback()
The callback can optionally be cancelled with:
+ fence_remove_callback()
To wait synchronously, optionally with a timeout:
+ fence_wait()
+ fence_wait_timeout()
A default software-only implementation is provided, which can be used
by drivers attaching a fence to a buffer when they have no other means
for hw sync. But a memory backed fence is also envisioned, because it
is common that GPU's can write to, or poll on some memory location for
synchronization. For example:
fence = custom_get_fence(...);
if ((seqno_fence = to_seqno_fence(fence)) != NULL) {
dma_buf *fence_buf = fence-sync_buf;
get_dma_buf(fence_buf);
... tell the hw the memory location to wait ...
custom_wait_on(fence_buf, fence-seqno_ofs, fence-seqno);
} else {
/* fall-back to sw sync * /
fence_add_callback(fence, my_cb);
}
On SoC platforms, if some other hw mechanism is provided for synchronizing
between IP blocks, it could be supported as an alternate implementation
with it's own fence ops in a similar way.
enable_signaling callback is used to provide sw signaling in case a cpu
waiter is requested or no compatible hardware signaling could be used.
The intention is to provide a userspace interface (presumably via eventfd)
later, to be used in conjunction with dma-buf's mmap support for sw access
to buffers (or for userspace apps that would prefer to do their own
synchronization).
v1: Original
v2: After discussion w/ danvet and mlankhorst on #dri-devel, we decided
that dma-fence didn't need to care about the sw-hw signaling path
(it can be handled same as sw-sw case), and therefore the fence-ops
can be simplified and more handled in the core. So remove the signal,
add_callback, cancel_callback, and wait ops, and replace with a simple
enable_signaling() op which can be used to inform a fence supporting
hw-hw signaling that one or more devices which do not support hw
signaling are waiting (and therefore it should enable an irq or do
whatever is necessary in order that the CPU is notified when the
fence is passed).
v3: Fix locking fail in attach_fence() and get_fence()
v4: Remove tie-in w/ dma-buf.. after discussion w/ danvet and mlankorst
we decided that we need to be able to attach one fence to N dma-buf's,
so using the list_head in dma-fence struct would be problematic.
v5: [ Maarten Lankhorst ] Updated for dma-bikeshed-fence and dma-buf-manager.
v6: [ Maarten Lankhorst ] I removed dma_fence_cancel_callback and some
comments
about checking if fence fired or not. This is broken by design.
waitqueue_active during destruction is now fatal, since the signaller
should be holding a reference in enable_signalling until it signalled
the fence. Pass the original dma_fence_cb along, and call __remove_wait
in the dma_fence_callback handler, so that no cleanup needs to be
performed.
v7: [ Maarten Lankhorst ] Set cb-func and only enable sw signaling if
fence wasn't signaled yet, for example for hardware fences that may
choose to signal blindly.
v8: [ Maarten Lankhorst ] Tons of tiny fixes, moved __dma_fence_init to
header and fixed include mess. dma-fence.h now includes dma-buf.h
All members are now initialized, so kmalloc can be used for
allocating a dma-fence. More documentation added.
v9: Change compiler bitfields to flags, change return type of
enable_signaling to bool. Rework dma_fence_wait. Added
dma_fence_is_signaled and dma_fence_wait_timeout.
s/dma// and change exports to non GPL. Added fence_is_signaled and
fence_enable_sw_signaling calls, add ability to
