[Intel-gfx] [PATCH] drm/i915/selftests: Wait until we start timeslicing after a submit

[Ruhl, Michael J]

>-----Original Message-----
>From: Chris Wilson <chris at chris-wilson.co.uk>
>Sent: Friday, April 3, 2020 4:34 PM
>To: Ruhl, Michael J <michael.j.ruhl at intel.com>; intel-
>gfx at lists.freedesktop.org
>Subject: Re: [Intel-gfx] [PATCH] drm/i915/selftests: Wait until we start
>timeslicing after a submit
>
>Quoting Ruhl, Michael J (2020-04-03 21:31:42)
>> >-----Original Message-----
>> >From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of
>Chris
>> >Wilson
>> >Sent: Friday, April 3, 2020 3:02 PM
>> >To: intel-gfx at lists.freedesktop.org
>> >Cc: Chris Wilson <chris at chris-wilson.co.uk>
>> >Subject: [Intel-gfx] [PATCH] drm/i915/selftests: Wait until we start
>timeslicing
>> >after a submit
>> >
>> >If we submit, we do not start timeslicnig until we process the CS event
>>
>> s/timeslicnig/timeslicing/
>>
>> >that marks the start of the context running on HW. So in the selftest,
>> >be sure to wait until we have processed the pending events before
>> >asserting that timeslicing has begun.
>> >
>> >Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>> >---
>> > drivers/gpu/drm/i915/gt/selftest_lrc.c | 6 +++++-
>> > 1 file changed, 5 insertions(+), 1 deletion(-)
>> >
>> >diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c
>> >b/drivers/gpu/drm/i915/gt/selftest_lrc.c
>> >index 985d4041d929..9e02917695b1 100644
>> >--- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
>> >+++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
>> >@@ -1244,7 +1244,11 @@ static int live_timeslice_queue(void *arg)
>> >               if (err)
>> >                       goto err_rq;
>> >
>> >-              intel_engine_flush_submission(engine);
>> >+              /* Wait until we ack the release_queue and start timeslicing
>> >*/
>> >+              do {
>> >+                      intel_engine_flush_submission(engine);
>> >+              } while (READ_ONCE(engine->execlists.pending[0]));
>>
>> Is this guaranteed to clear?  Or should there be a count to protect against
>> the endless loop?
>
>Yes. If the HW stops, we reset it and clear the submission queue.

In that case:

Acked-by: Michael J. Ruhl <michael.j.ruhl at intel.com>

M

>-Chris