Quoting Mika Kuoppala (2017-10-27 07:44:31) > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > > > An interesting snippet from Sandybridge's prm: > > > > "Although a Ring Buffer can be enabled in the non-empty state, it must > > not be disabled unless it is empty. Attempting to disable a Ring Buffer > > in the non-empty state is UNDEFINED." > > > > Let's avoid the undefined behaviour as we disable the rings prior to > > reset and resume. > > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> > > --- > > drivers/gpu/drm/i915/intel_ringbuffer.c | 4 +++- > > drivers/gpu/drm/i915/intel_uncore.c | 4 +++- > > 2 files changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c > > index 05e01446b00b..3f2073a9d37a 100644 > > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c > > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c > > @@ -480,10 +480,12 @@ static bool stop_ring(struct intel_engine_cs *engine) > > } > > } > > > > - I915_WRITE_CTL(engine, 0); > > I915_WRITE_HEAD(engine, 0); > > I915_WRITE_TAIL(engine, 0); > > > > + /* The ring must be empty before it is disabled */ > > + I915_WRITE_CTL(engine, 0); > > + > > I am thinking that does it need even more finesse. I thought so too, but we already stop the ring, and so gave up thinking. > Like > > I915_WRITE_HEAD(engine, I915_READ_TAIL(engine)); Nevertheless, I'll give that a spin since that's neat ;) -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
