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<b><a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO --- - [SNB, IVB] Page flips hang indefinitely, apparently waiting for mmio writes that never happen"
href="https://bugs.freedesktop.org/show_bug.cgi?id=75502#c26">Comment # 26</a>
on <a class="bz_bug_link
bz_status_NEEDINFO "
title="NEEDINFO --- - [SNB, IVB] Page flips hang indefinitely, apparently waiting for mmio writes that never happen"
href="https://bugs.freedesktop.org/show_bug.cgi?id=75502">bug 75502</a>
from <span class="vcard"><a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> <span class="fn">Chris Wilson</span></a>
</span></b>
<pre>They confirm that the dspsurf is still at 0x00372000. The earlier theories that
another write happened are debunked. So it has to be something in the simple
MI_DISPLAY_FLIP command packets that causes the CS to simply ignore it.
Try,
diff --git a/drivers/gpu/drm/i915/intel_display.c
b/drivers/gpu/drm/i915/intel_display.c
index 0326ea8..1a680bf 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8842,6 +8842,10 @@ static int intel_gen6_queue_flip(struct drm_device *dev,
if (ret)
goto err;
+ ret = intel_ring_cacheline_align(ring);
+ if (ret)
+ goto err_unpin;
+
ret = intel_ring_begin(ring, 4);
if (ret)
goto err_unpin;
(current drm-intel-nightly already has that for ivb)</pre>
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