[Intel-gfx] [PATCH v10 1/6] drm/i915: Add per context timelines for fence objects

[Maarten Lankhorst]

Op 16-06-16 om 14:54 schreef John.C.Harrison at Intel.com:
> From: John Harrison <John.C.Harrison at Intel.com>
>
> The purpose of this patch series is to convert the requst structure to
> use fence objects for the underlying completion tracking. The fence
> object requires a sequence number. The ultimate aim is to use the same
> sequence number as for the request itself (or rather, to remove the
> request's seqno field and just use the fence's value throughout the
> driver). However, this is not currently possible and so this patch
> introduces a separate numbering scheme as an intermediate step.
>
> A major advantage of using the fence object is that it can be passed
> outside of the i915 driver and used externally. The fence API allows
> for various operations such as combining multiple fences. This
> requires that fence seqnos within a single fence context be guaranteed
> in-order. The GPU scheduler that is coming can re-order request
> execution but not within a single GPU context. Thus the fence context
> must be tied to the i915 context (and the engine within the context as
> each engine runs asynchronously).
>
> On the other hand, the driver as a whole currently only works with
> request seqnos that are allocated from a global in-order timeline. It
> will require a fair chunk of re-work to allow multiple independent
> seqno timelines to be used. Hence the introduction of a temporary,
> fence specific timeline. Once the work to update the rest of the
> driver has been completed then the request can use the fence seqno
> instead.
>
> v2: New patch in series.
>
> v3: Renamed/retyped timeline structure fields after review comments by
> Tvrtko Ursulin.
>
> Added context information to the timeline's name string for better
> identification in debugfs output.
>
> v5: Line wrapping and other white space fixes to keep style checker
> happy.
>
> v7: Updated to newer nightly (lots of ring -> engine renaming).
>
> v8: Moved to earlier in patch series so no longer needs to remove the
> quick hack timeline that was being added before.
>
> v9: Updated to another newer nightly (changes to context structure
> naming). Also updated commit message to match previous changes.
>
> v10: Removed obsolete fields from timeline structure and a couple of
> functions. Corrected some comments and debug prints. [Review comments
> from Maarten Lankhorst & Tvrtko Ursulin]
>
> Updated to yet more nightly changes (u64 for fence context).
>
> For: VIZ-5190
> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>

Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>