[Intel-gfx] [PATCH] drm/i915: Double check ring is idle before declaring the GPU wedged

[Chris Wilson]

On Mon, Aug 11, 2014 at 10:30:09AM +0100, Damien Lespiau wrote:
> On Mon, Aug 11, 2014 at 09:21:35AM +0100, Chris Wilson wrote:
> > During ring initialisation, sometimes we observe, though not in
> > production hardware, that the idle flag is not set even though the ring
> > is empty. Double check before giving up.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Damien Lespiau <damien.lespiau at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_ringbuffer.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > index a0831c309eab..d72d5e0e693d 100644
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > @@ -467,7 +467,12 @@ static bool stop_ring(struct intel_engine_cs *ring)
> >  		I915_WRITE_MODE(ring, _MASKED_BIT_ENABLE(STOP_RING));
> >  		if (wait_for((I915_READ_MODE(ring) & MODE_IDLE) != 0, 1000)) {
> >  			DRM_ERROR("%s : timed out trying to stop ring\n", ring->name);
> > -			return false;
> > +			/* Sometimes we observe that the idle flag is not
> > +			 * set even though the ring is empty. So double
> > +			 * check before giving up.
> > +			 */
> > +			if (I915_READ_HEAD(ring) != I915_READ_TAIL(ring))
> > +				return false;
> 
> That means we propably want to just put the user visible error message
> there as well?

It is still a 1 second timeout, so having a warning there that something
is wrong is important I thought.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre