Re: [Intel-gfx] [PATCH 1/2] drm/i915: Disable semaphore inter-engine sync without timeslicing

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 21/05/2020 09:53, Chris Wilson wrote:
> Since the remove of the no-semaphore boosting, we rely on timeslicing to
> reorder past inter-dependency hogs across the engines. However, we
> require preemption to support timeslicing into user payloads, and not all
> machine support preemption so we do not universally enable timeslicing
> even when it would preempt our own inter-engine semaphores.
> 
> Testcase: igt/gem_exec_schedule/semaphore-codependency # bdw/bsw
> Fixes: 18e4af04d218 ("drm/i915: Drop no-semaphore boosting")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_context.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index 900ea8b7fc8f..f5d59d18cd5b 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -230,7 +230,7 @@ static void intel_context_set_gem(struct intel_context *ce,
>   		ce->timeline = intel_timeline_get(ctx->timeline);
>   
>   	if (ctx->sched.priority >= I915_PRIORITY_NORMAL &&
> -	    intel_engine_has_semaphores(ce->engine))
> +	    intel_engine_has_timeslices(ce->engine))
>   		__set_bit(CONTEXT_USE_SEMAPHORES, &ce->flags);
>   }
>   
> @@ -1969,7 +1969,7 @@ static int __apply_priority(struct intel_context *ce, void *arg)
>   {
>   	struct i915_gem_context *ctx = arg;
>   
> -	if (!intel_engine_has_semaphores(ce->engine))
> +	if (!intel_engine_has_timeslices(ce->engine))
>   		return 0;
>   
>   	if (ctx->sched.priority >= I915_PRIORITY_NORMAL)
> 

__i915_request_await_execution is okay to keep using semaphores?

Regards,

Tvrtko
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