Re: [PATCH 13/51] drm/i915/guc: Disable semaphores when using GuC scheduling

[John Harrison <john.c.harrison@intel.com>]

On 7/16/2021 13:16, Matthew Brost wrote:
> Semaphores are an optimization and not required for basic GuC submission
> to work properly. Disable until we have time to do the implementation to
> enable semaphores and tune them for performance. Also long direction is
> just to delete semaphores from the i915 so another reason to not enable
> these for GuC submission.
>
> This patch fixes an existing bug where I915_ENGINE_HAS_SEMAPHORES was
> not honored correctly.
Bugs plural. Otherwise:
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>

>
> v2: Reword commit message
> v3:
>   (John H)
>    - Add text to commit indicating this also fixing an existing bug
>
> Cc: John Harrison <john.c.harrison@intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_context.c | 6 ++++--
>   1 file changed, 4 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 7d6f52d8a801..64659802d4df 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -799,7 +799,8 @@ static int intel_context_set_gem(struct intel_context *ce,
>   	}
>   
>   	if (ctx->sched.priority >= I915_PRIORITY_NORMAL &&
> -	    intel_engine_has_timeslices(ce->engine))
> +	    intel_engine_has_timeslices(ce->engine) &&
> +	    intel_engine_has_semaphores(ce->engine))
>   		__set_bit(CONTEXT_USE_SEMAPHORES, &ce->flags);
>   
>   	if (IS_ACTIVE(CONFIG_DRM_I915_REQUEST_TIMEOUT) &&
> @@ -1778,7 +1779,8 @@ static void __apply_priority(struct intel_context *ce, void *arg)
>   	if (!intel_engine_has_timeslices(ce->engine))
>   		return;
>   
> -	if (ctx->sched.priority >= I915_PRIORITY_NORMAL)
> +	if (ctx->sched.priority >= I915_PRIORITY_NORMAL &&
> +	    intel_engine_has_semaphores(ce->engine))
>   		intel_context_set_use_semaphores(ce);
>   	else
>   		intel_context_clear_use_semaphores(ce);