i915_gem_handle_seqno_wrap() will zero all sync_seqnos but as the
wrap can happen inside ring->sync_to(), pre wrap seqno was
carried over and overwrote the zeroed sync_seqno.
When wrap is handled, all outstanding requests will be retired and
objects moved to inactive queue, causing their last_read_seqno to be zero.
Use this to update the sync_seqno correctly.
RING_SYNC registers after wrap will contain pre wrap values which
are >= seqno. So injecting the semaphore wait into ring completes
immediately.
Original idea for using last_read_seqno from Chris Wilson.
Signed-off-by: Mika Kuoppala <mika.kuopp...@intel.com>
Reviewed-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/i915_gem.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 85a0948..4ef8b57 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2397,7 +2397,11 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj,
ret = to->sync_to(to, from, seqno);
if (!ret)
- from->sync_seqno[idx] = seqno;
+ /* We use last_read_seqno because sync_to()
+ * might have just caused seqno wrap under
+ * the radar.
+ */
+ from->sync_seqno[idx] = obj->last_read_seqno;
return ret;
}
--
1.7.9.5
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