On Thu, May 12, 2016 at 10:06:31PM +0100, John.C.Harrison@xxxxxxxxx wrote:
> From: John Harrison <John.C.Harrison@xxxxxxxxx>
>
> The fence object used inside the request structure requires a sequence
> number. Although this is not used by the i915 driver itself, it could
> potentially be used by non-i915 code if the fence is passed outside of
> the driver. This is the intention as it allows external kernel drivers
> and user applications to wait on batch buffer completion
> asynchronously via the dma-buff fence API.
>
> To ensure that such external users are not confused by strange things
> happening with the seqno, this patch adds in a per context timeline
> that can provide a guaranteed in-order seqno value for the fence. This
> is safe because the scheduler will not re-order batch buffers within a
> context - they are considered to be mutually dependent.
>
> 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.
>
> For: VIZ-5190
> Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 14 ++++++++++++
> drivers/gpu/drm/i915/i915_gem.c | 40 +++++++++++++++++++++++++++++++++
> drivers/gpu/drm/i915/i915_gem_context.c | 14 ++++++++++++
> drivers/gpu/drm/i915/intel_lrc.c | 8 +++++++
> 4 files changed, 76 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index d5496ab..520480b 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -818,6 +818,19 @@ struct i915_ctx_hang_stats {
> bool banned;
> };
>
> +struct i915_fence_timeline {
> + char name[32];
> + unsigned fence_context;
> + unsigned next;
> +
> + struct intel_context *ctx;
> + struct intel_engine_cs *engine;
> +};
> +
> +int i915_create_fence_timeline(struct drm_device *dev,
> + struct intel_context *ctx,
> + struct intel_engine_cs *ring);
> +
> /* This must match up with the value previously used for execbuf2.rsvd1. */
> #define DEFAULT_CONTEXT_HANDLE 0
>
> @@ -869,6 +882,7 @@ struct intel_context {
> u64 lrc_desc;
> uint32_t *lrc_reg_state;
> bool initialised;
> + struct i915_fence_timeline fence_timeline;
This is still fundamentally wrong. This i915_fence_timeline is both the
fence context and timeline. Our timelines are singular per vm, with a
fence context under each timeline per engine.
Please complete the legacy/execlists unification first so that we can
have timelines work correctly for the whole driver.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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