On Wed, Apr 06, 2016 at 12:32:29PM +0300, Mika Kuoppala wrote:
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
>
> > [ text/plain ]
> > Having fixed the tracking of the engine's last_submitted_seqno, we can
> > now rely on it for detecting when the engine is idle (and not have to
> > touch the requests pointer).
> >
> > Testcase: igt/gem_exec_whisper
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_irq.c | 3 +--
> > 1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index c85eb8dec2dc..a56be4f92264 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -2805,8 +2805,7 @@ static void gen8_disable_vblank(struct drm_device *dev, unsigned int pipe)
> > static bool
> > ring_idle(struct intel_engine_cs *engine, u32 seqno)
> > {
> > - return (list_empty(&engine->request_list) ||
> > - i915_seqno_passed(seqno, engine->last_submitted_seqno));
> > + return i915_seqno_passed(seqno, engine->last_submitted_seqno);
>
> My concern here is that we should move the write for the
> last_submitted_seqno before we push the work into ring.
>
> To guarantee that the driver never sees a seqno > last_submitted_seqno
> on particular ring.
Reasonable request. You'll want a smp_store_mb() on the
last_submitted_seqno as well with a comment
/* barrier for hangcheck */
In return what's up with the Braswell?
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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