[Intel-gfx] [PATCH 1/2] drm/i915/guc: Advance over port[0] if set and not preempting

[Chris Wilson]

Quoting Chris Wilson (2017-11-24 13:37:44)
> Our execlist emulation is intended to only use a maximum of 2 ports per
> engine, so as to not overflow the wq. (By knowing the limits, we can
> avoid having to handle the wq exhaustion.) However, upon adding
> preemption, we lost the skip over the first port if set for the
> non-preemption path. Restore it.
> 
> Reported-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Fixes: c41937fd994a ("drm/i915/guc: Preemption! With GuC")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Michał Winiarski <michal.winiarski at intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_guc_submission.c | 29 ++++++++++++++++-------------
>  1 file changed, 16 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
> index cbf5a96f5806..70e64bdb73dd 100644
> --- a/drivers/gpu/drm/i915/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/intel_guc_submission.c
> @@ -743,23 +743,26 @@ static void guc_dequeue(struct intel_engine_cs *engine)
>         if (!rb)
>                 goto unlock;
>  
> -       if (HAS_LOGICAL_RING_PREEMPTION(engine->i915) && port_isset(port)) {
> -               struct guc_preempt_work *preempt_work =
> -                       &engine->i915->guc.preempt_work[engine->id];
> -
> -               if (rb_entry(rb, struct i915_priolist, node)->priority >
> -                   max(port_request(port)->priotree.priority, 0)) {
> -                       execlists_set_active(execlists,
> -                                            EXECLISTS_ACTIVE_PREEMPT);
> -                       queue_work(engine->i915->guc.preempt_wq,
> -                                  &preempt_work->work);
> -                       goto unlock;
> -               } else if (port_isset(last_port)) {
> -                       goto unlock;
> +       if (port_isset(port)) {
> +               if (HAS_LOGICAL_RING_PREEMPTION(engine->i915)) {
> +                       struct guc_preempt_work *preempt_work =
> +                               &engine->i915->guc.preempt_work[engine->id];
> +
> +                       if (rb_entry(rb, struct i915_priolist, node)->priority >
> +                           max(port_request(port)->priotree.priority, 0)) {
> +                               execlists_set_active(execlists,
> +                                                    EXECLISTS_ACTIVE_PREEMPT);
> +                               queue_work(engine->i915->guc.preempt_wq,
> +                                          &preempt_work->work);
> +                               goto unlock;
> +                       }
>                 }
>  
>                 port++;
> +               if (port_isset(port))

You probably want to stick with last_port, or at least Mika will want to
make it last_port again after he expands ELSP[] and propagates all the
changes.
-Chris