On Thu, 7 Aug 2014, Jiri Kosina wrote: > The patch below seems to finally cure the problem at my system; I've just > attached it to freedesktop bugzilla, but sending it to this thread as well > to hopefully get as much testing coverage by affected people as possible. > > I am going on with testing whether it really completely fixes the problem > or just made it less likely. Okay, after 31 suspend-resume cycles, the problem appeared again (while without the patch, it triggers with 100% reliability). So it's not a complete fix, it just makes the problem much less visible. Going back to bugzilla discussion. > > From: Jiri Kosina <jkosina@xxxxxxx> > Subject: [PATCH] drm/i915: read HEAD register back in init_ring_common() to enforce ordering > > Withtout this, ring initialization fails reliabily during resume with > > [drm:init_ring_common] *ERROR* render ring initialization failed ctl 0001f001 head ffffff8804 tail 00000000 start 000e4000 > > Signed-off-by: Jiri Kosina <jkosina@xxxxxxx> > --- > drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c > index 279488a..7add7ee 100644 > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c > @@ -517,6 +517,9 @@ static int init_ring_common(struct intel_engine_cs *ring) > else > ring_setup_phys_status_page(ring); > > + /* Enforce ordering by reading HEAD register back */ > + I915_READ_HEAD(ring); > + > /* Initialize the ring. This must happen _after_ we've cleared the ring > * registers with the above sequence (the readback of the HEAD registers > * also enforces ordering), otherwise the hw might lose the new ring -- Jiri Kosina SUSE Labs _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
