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@xxxxxxxxxxxxxxx>
> Fixes: c41937fd994a ("drm/i915/guc: Preemption! With GuC")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> 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
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