[Intel-gfx] [PATCH 1/3] drm/i915/execlists: Lift opportunistic process_csb to before engine lock

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Since the process_csb() does not require us to hold the
> engine->active.lock, we can move the opportunistic flush before
> direction submission to outside of the lock.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

Reviewed-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/gt/intel_lrc.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 5ab0ed35af84..e866b8d721ed 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -3170,13 +3170,6 @@ static void __submit_queue_imm(struct intel_engine_cs *engine)
>  	if (reset_in_progress(execlists))
>  		return; /* defer until we restart the engine following reset */
>  
> -	/* Hopefully we clear execlists->pending[] to let us through */
> -	if (READ_ONCE(execlists->pending[0]) &&
> -	    tasklet_trylock(&execlists->tasklet)) {
> -		process_csb(engine);
> -		tasklet_unlock(&execlists->tasklet);
> -	}
> -
>  	__execlists_submission_tasklet(engine);
>  }
>  
> @@ -3199,11 +3192,25 @@ static bool ancestor_on_hold(const struct intel_engine_cs *engine,
>  	return !list_empty(&engine->active.hold) && hold_request(rq);
>  }
>  
> +static void flush_csb(struct intel_engine_cs *engine)
> +{
> +	struct intel_engine_execlists *el = &engine->execlists;
> +
> +	if (READ_ONCE(el->pending[0]) && tasklet_trylock(&el->tasklet)) {
> +		if (!reset_in_progress(el))
> +			process_csb(engine);
> +		tasklet_unlock(&el->tasklet);
> +	}
> +}
> +
>  static void execlists_submit_request(struct i915_request *request)
>  {
>  	struct intel_engine_cs *engine = request->engine;
>  	unsigned long flags;
>  
> +	/* Hopefully we clear execlists->pending[] to let us through */
> +	flush_csb(engine);
> +
>  	/* Will be called from irq-context when using foreign fences. */
>  	spin_lock_irqsave(&engine->active.lock, flags);
>  
> -- 
> 2.20.1
>
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