[Intel-gfx] [PATCH] drm/i915: Reset the breadcrumbs IRQ more carefully

[Chris Wilson]

On Thu, Oct 06, 2016 at 04:32:37PM +0300, Mika Kuoppala wrote:
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > Along with the interrupt, we want to restore the fake-irq and
> > wait-timeout detection. If we use the breadcrumbs interface to setup the
> > interrupt as it wants, the auxiliary timers will also be restored.
> >
> > Fixes: 821ed7df6e2a ("drm/i915: Update reset path to fix incomplete requests")
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Mika Kuoppala <mika.kuoppala at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_breadcrumbs.c | 17 +++++++++++++++++
> >  drivers/gpu/drm/i915/intel_engine_cs.c   | 15 ---------------
> >  drivers/gpu/drm/i915/intel_lrc.c         |  2 +-
> >  drivers/gpu/drm/i915/intel_ringbuffer.c  |  2 +-
> >  drivers/gpu/drm/i915/intel_ringbuffer.h  |  2 +-
> >  5 files changed, 20 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
> > index 9dba4971fb1e..d27da6d69735 100644
> > --- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
> > +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
> > @@ -584,6 +584,23 @@ int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine)
> >  	return 0;
> >  }
> >  
> > +void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine)
> > +{
> > +	struct intel_breadcrumbs *b = &engine->breadcrumbs;
> > +
> 
> Should we kill the timer before proceeding in here?

Which timer? In breadcrumbs.c, we are concerned with the fake_irq and
the wait-timeout. The wait-timeout is reset below, we should add the
code to cancel the fake_irq along with clearing the bit.
 
> Not relevant to this patch but I also noticed that the period
> is identical to hangcheck period. Multiple of hangcheck period
> would be better, as our kicking might help and we don't
> want to fallback to fake irqs just so easily.

?

The main GPU hangcheck is kicked off by the wait timeout. Keeping the
two pieces independent (fake-irq, hangcheck) is quite nice, and the
jiffie wake up serves as a backup, and either it is required or it will
be disabled by the reset.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre