14 Jan
2020
14 Jan
'20
2:25 p.m.
Am 14.01.20 um 13:19 schrieb Lionel Landwerlin:
We've added a set of new APIs to manipulate syncobjs holding timelines of dma_fence. This adds a bit of documentation about how this works.
v2: Small language nits (Lionel)
Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com Cc: Christian Koenig Christian.Koenig@amd.com Cc: Jason Ekstrand jason@jlekstrand.net Cc: David(ChunMing) Zhou David1.Zhou@amd.com
Reviewed-by: Christian König christian.koenig@amd.com
drivers/gpu/drm/drm_syncobj.c | 87 +++++++++++++++++++++++++++++------ 1 file changed, 74 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c index 669c93fe2500..42d46414f767 100644 --- a/drivers/gpu/drm/drm_syncobj.c +++ b/drivers/gpu/drm/drm_syncobj.c @@ -43,27 +43,66 @@
- Signal a syncobj (set a trivially signaled fence)
- Wait for a syncobj's fence to appear and be signaled
- The syncobj userspace API also provides operations to manipulate a syncobj
- in terms of a timeline of struct &dma_fence_chain rather than a single
- struct &dma_fence, through the following operations:
- Signal a given point on the timeline
- Wait for a given point to appear and/or be signaled
- Import and export from/to a given point of a timeline
- At it's core, a syncobj is simply a wrapper around a pointer to a struct
- &dma_fence which may be NULL.
- When a syncobj is first created, its pointer is either NULL or a pointer
- to an already signaled fence depending on whether the
- &DRM_SYNCOBJ_CREATE_SIGNALED flag is passed to
- &DRM_IOCTL_SYNCOBJ_CREATE.
- When GPU work which signals a syncobj is enqueued in a DRM driver,
- the syncobj fence is replaced with a fence which will be signaled by the
- completion of that work.
- When GPU work which waits on a syncobj is enqueued in a DRM driver, the
- driver retrieves syncobj's current fence at the time the work is enqueued
- waits on that fence before submitting the work to hardware.
- If the syncobj's fence is NULL, the enqueue operation is expected to fail.
- All manipulation of the syncobjs's fence happens in terms of the current
- fence at the time the ioctl is called by userspace regardless of whether
- that operation is an immediate host-side operation (signal or reset) or
- or an operation which is enqueued in some driver queue.
- &DRM_IOCTL_SYNCOBJ_RESET and &DRM_IOCTL_SYNCOBJ_SIGNAL can be used to
- manipulate a syncobj from the host by resetting its pointer to NULL or
- If the syncobj is considered as a binary (its state is either signaled or
- unsignaled) primitive, when GPU work is enqueued in a DRM driver to signal
- the syncobj, the syncobj's fence is replaced with a fence which will be
- signaled by the completion of that work.
- If the syncobj is considered as a timeline primitive, when GPU work is
- enqueued in a DRM driver to signal the a given point of the syncobj, a new
- struct &dma_fence_chain pointing to the DRM driver's fence and also
- pointing to the previous fence that was in the syncobj. The new struct
- &dma_fence_chain fence replace the syncobj's fence and will be signaled by
- completion of the DRM driver's work and also any work associated with the
- fence previously in the syncobj.
- When GPU work which waits on a syncobj is enqueued in a DRM driver, at the
- time the work is enqueued, it waits on the syncobj's fence before
- submitting the work to hardware. That fence is either :
- The syncobj's current fence if the syncobj is considered as a binary
primitive.
- The struct &dma_fence associated with a given point if the syncobj is
considered as a timeline primitive.
- If the syncobj's fence is NULL or not present in the syncobj's timeline,
- the enqueue operation is expected to fail.
- With binary syncobj, all manipulation of the syncobjs's fence happens in
- terms of the current fence at the time the ioctl is called by userspace
- regardless of whether that operation is an immediate host-side operation
- (signal or reset) or or an operation which is enqueued in some driver
- queue. &DRM_IOCTL_SYNCOBJ_RESET and &DRM_IOCTL_SYNCOBJ_SIGNAL can be used
- to manipulate a syncobj from the host by resetting its pointer to NULL or
- setting its pointer to a fence which is already signaled.
- With a timeline syncobj, all manipulation of the synobj's fence happens in
- terms of a u64 value referring to point in the timeline. See
- dma_fence_chain_find_seqno() to see how a given point is found in the
- timeline.
- Note that applications should be careful to always use timeline set of
- ioctl() when dealing with syncobj considered as timeline. Using a binary
- set of ioctl() with a syncobj considered as timeline could result incorrect
- synchronization. The use of binary syncobj is supported through the
- timeline set of ioctl() by using a point value of 0, this will reproduce
- the behavior of the binary set of ioctl() (for example replace the
- syncobj's fence when signaling).
- Host-side wait on syncobjs
@@ -87,6 +126,16 @@
- synchronize between the two.
- This requirement is inherited from the Vulkan fence API.
- Similarly, &DRM_IOCTL_SYNCOBJ_TIMELINE_WAIT takes an array of syncobj
- handles as well as an array of u64 points and does a host-side wait on all
- of syncobj fences at the given points simultaneously.
- &DRM_IOCTL_SYNCOBJ_TIMELINE_WAIT also adds the ability to wait for a given
- fence to materialize on the timeline without waiting for the fence to be
- signaled by using the &DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE flag. This
- requirement is inherited from the wait-before-signal behavior required by
- the Vulkan timeline semaphore API.
- Import/export of syncobjs
@@ -120,6 +169,18 @@
- Because sync files are immutable, resetting or signaling the syncobj
- will not affect any sync files whose fences have been imported into the
- syncobj.
- Import/export of timeline points in timeline syncobjs
- &DRM_IOCTL_SYNCOBJ_TRANSFER provides a mechanism to transfer a struct
- &dma_fence_chain of a syncobj at a given u64 point to another u64 point
- into another syncobj.
- Note that if you want to transfer a struct &dma_fence_chain from a given
- point on a timeline syncobj from/into a binary syncobj, you can use the
- point 0 to mean take/replace the fence in the syncobj.
*/
#include <linux/anon_inodes.h>