From: John Harrison <John.C.Harrison@xxxxxxxxx> There is a construct in the linux kernel called 'struct fence' that is intended to keep track of work that is executed on hardware. I.e. it solves the basic problem that the drivers 'struct drm_i915_gem_request' is trying to address. The request structure does quite a lot more than simply track the execution progress so is very definitely still required. However, the basic completion status side could be updated to use the ready made fence implementation and gain all the advantages that provides. Using the struct fence object also has the advantage that the fence can be used outside of the i915 driver (by other drivers or by userland applications). That is the basis of the dma-buff synchronisation API and allows asynchronous tracking of work completion. In this case, it allows applications to be signalled directly when a batch buffer completes without having to make an IOCTL call into the driver. Note that in order to allow the full fence API to be used (e.g. merging multiple fences together), the driver needs to provide an incrementing timeline for the fence. Currently this timeline is specific to the fence code as it must be per context. There is future work planned to make the driver's internal seqno value also be per context rather than driver global (VIZ-7443). Once this is done the fence specific timeline code can be dropped in favour of just using the driver's seqno value. This is work that was planned since the conversion of the driver from being seqno value based to being request structure based. This patch series does that work. An IGT test to exercise the fence support from user land is in progress and will follow. Android already makes extensive use of fences for display composition. Real world linux usage is planned in the form of Jesse's page table sharing / bufferless execbuf support. There is also a plan that Wayland (and others) could make use of it in a similar manner to Android. v2: Updated for review comments by various people and to add support for Android style 'native sync'. v3: Updated from review comments by Tvrtko Ursulin. Also moved sync framework out of staging and improved request completion handling. v4: Fixed patch tag (should have been PATCH not RFC). Corrected ownership of one patch which had passed through many hands before reaching me. Fixed a bug introduced in v3 and updated for review comments. v5: Removed de-staging and further updates to Android sync code. The de-stage is now being handled by someone else. The sync integration to the i915 driver will be a separate patch set that can only land after the external de-stage has been completed. Assorted changes based on review comments and style checker fixes. Most significant change is fixing up the fake lost interrupt support for the 'drv_missed_irq_hang' IGT test and improving the wait request latency. v6: Updated to newer nigthly and resolved conflicts around updates to the wait_request optimisations. v7: Updated to newer nightly and resolved conflicts around massive ring -> engine rename and interface change to get_seqno(). Also fixed up a race condition issue with stale request pointers in file client lists and added a minor optimisation to not acquire spinlocks when a list is empty and does not need processing. v8: Updated to yet another nightly and resolved the merge conflicts. Dropped 'delay freeing of requests' patch as no longer needed to due changes in request clean up code. Likewise with the deferred processing of the fence signalling. Also moved the fence timeline patch to before the fence conversion. It now means the timeline is initially added with no actual user but also means the fence conversion patch does not need to add a horrid hack timeline which is then removed again in a subsequent patch. Added support for possible RCU usage of fence object (Review comments by Maarten Lankhorst). v9: Updated to another newer nightly (changes to context structure naming). Moved the request completion processing out of the interrupt handler and into a worker thread (Chris Wilson). v10: Removed obsolete fields from timeline structure and a couple of functions. Corrected some comments and debug prints. Removed duplicate rcu_head field from request - there is already one in the fence structure for this exact purpose. Improved/added some comments and WARNs. Changed to an un-ordered work queue to allow parallel processing of different engines. Also set the high priority flag for reduced latency. Removed some unnecessary checks for invalid seqno values. Moved a spinlock release a few lines later to make the 'locked' parameter of i915_gem_request_enable_interrupt redundant and removed it. Also shuffled the function around in the file so as to make it static and remove it from the header file. Corrected the use of fence_signal_locked() to fence_signal() in the retire code. Dropped the irq save part of the spin lock calls in the notify code as this is no longer called from the ISR. Changed the call of i915_gem_retire_requests_ring() in the reset cleanup code to i915_gem_request_notify() instead as the former is just duplicating a lot of operations. Dropped the 'is_empty' flag from trace_i915_gem_request_notify() as it is now redundant - 'seqno == 0' is equivalent. [Review comments from Maarten Lankhorst & Tvrtko Ursulin] Added extra checks and re-instated the lazy_coherency flag to the call of i915_gem_request_notify() from i915_gem_retire_requests_ring() on the grounds that it happens lots and lots and mostly does not actually need to do anything. Updated for yet more nightly changes (u64 for fence context). [Patches against drm-intel-nightly tree fetched 09/06/2016] John Harrison (6): drm/i915: Add per context timelines for fence objects drm/i915: Convert requests to use struct fence drm/i915: Removed now redundant parameter to i915_gem_request_completed() drm/i915: Interrupt driven fences drm/i915: Updated request structure tracing drm/i915: Cache last IRQ seqno to reduce IRQ overhead drivers/gpu/drm/i915/i915_debugfs.c | 7 +- drivers/gpu/drm/i915/i915_dma.c | 14 +- drivers/gpu/drm/i915/i915_drv.h | 61 ++--- drivers/gpu/drm/i915/i915_gem.c | 412 ++++++++++++++++++++++++++++++-- drivers/gpu/drm/i915/i915_gem_context.c | 16 ++ drivers/gpu/drm/i915/i915_irq.c | 3 +- drivers/gpu/drm/i915/i915_trace.h | 6 +- drivers/gpu/drm/i915/intel_display.c | 2 +- drivers/gpu/drm/i915/intel_lrc.c | 14 ++ drivers/gpu/drm/i915/intel_pm.c | 4 +- drivers/gpu/drm/i915/intel_ringbuffer.c | 6 + drivers/gpu/drm/i915/intel_ringbuffer.h | 12 + 12 files changed, 492 insertions(+), 65 deletions(-) -- 1.9.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
