[Intel-gfx] [PATCH] i915/pmu: Move execlist stats initialization to execlist specific setup

[Teres Alexis, Alan Previn]

I went up the call stack to ensure the differences between the
old and new location isnt skipping over other functions that may reference
something engine related (that may also end up triggering stats variabls).

Without digging further, i see the old postion here:
i915_driver_probe -> i915_driver_mmio_probe -> intel_gt_init_mmio -> intel_engines_init_mmio -> intel_engine_setup
new postion here:
i915_driver_probe -> i915_gem_init -> (for_each_gt) intel_gt_init -> intel_engines_init -> setup (intel_execlists_submission_setup)

And between i915_driver_mmio_probe and i915_gem_init are only mem/ggtt, display and irq related init functions.
That said, LGTM (although you do need to address the BAT failure before merging):

Reviewed-by: Alan Previn <alan.previn.teres.alexis at intel.com>

On Tue, 2023-09-12 at 14:22 -0700, Umesh Nerlige Ramappa wrote:
> engine->stats is a union of execlist and guc stat objects. When execlist
> specific fields are initialized, the initial state of guc stats is
> affected. This results in bad busyness values when using GuC mode. Move
> the execlist initialization from common code to execlist specific code.
> 
> Fixes: 77cdd054dd2c ("drm/i915/pmu: Connect engine busyness stats from GuC to pmu")
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_engine_cs.c            | 1 -
>  drivers/gpu/drm/i915/gt/intel_execlists_submission.c | 2 ++
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index dfb69fc977a0..84a75c95f3f7 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -558,7 +558,6 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id,
>  		DRIVER_CAPS(i915)->has_logical_contexts = true;
>  
>  	ewma__engine_latency_init(&engine->latency);
> -	seqcount_init(&engine->stats.execlists.lock);
>  
>  	ATOMIC_INIT_NOTIFIER_HEAD(&engine->context_status_notifier);
>  
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index 4d05321dc5b5..e8f42ec6b1b4 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -3548,6 +3548,8 @@ int intel_execlists_submission_setup(struct intel_engine_cs *engine)
>  	logical_ring_default_vfuncs(engine);
>  	logical_ring_default_irqs(engine);
>  
> +	seqcount_init(&engine->stats.execlists.lock);
> +
>  	if (engine->flags & I915_ENGINE_HAS_RCS_REG_STATE)
>  		rcs_submission_override(engine);
>