On Mon, Aug 11, 2014 at 11:07:10AM +0100, Damien Lespiau wrote:
> On Mon, Aug 11, 2014 at 10:35:25AM +0100, Chris Wilson wrote:
> > 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@xxxxxxxxxxxxxxxxxx>
> > > > Cc: Damien Lespiau <damien.lespiau@xxxxxxxxx>
> > > > ---
> > > > 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.
>
> Ah, I missed the "not in production hw" bits of the commit message, It
> may mean simulation and then the guess is that flag is not implemented.
> If that makes us not totally give up, I guess that's something.
I was trying to avoid saying that it was only to work around sim bugs :)
Otherwise, it looks to be a useful piece of paranoia and logging against
hw trying to screw us over.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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