From: Ville Syrjälä <ville.syrj...@linux.intel.com>

According to BSpec the entire MI_DISPLAY_FLIP packet must be contained
in a single cacheline. Make sure that happens.

v2: Use intel_ring_begin_cacheline_safe()
v3: Use intel_ring_cacheline_align() (Chris)

Cc: Bjoern C <l...@call-home.ch>
Cc: Alexandru DAMIAN <alexandru.dam...@intel.com>
Cc: Enrico Tagliavini <enrico.tagliav...@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=74053
Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index 0c25310..37527d4 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8609,6 +8609,20 @@ static int intel_gen7_queue_flip(struct drm_device *dev,
        if (ring->id == RCS)
                len += 6;
 
+       /*
+        * BSpec MI_DISPLAY_FLIP for IVB:
+        * "The full packet must be contained within the same cache line."
+        *
+        * Currently the LRI+SRM+MI_DISPLAY_FLIP all fit within the same
+        * cacheline, if we ever start emitting more commands before
+        * the MI_DISPLAY_FLIP we may need to first emit everything else,
+        * then do the cacheline alignment, and finally emit the
+        * MI_DISPLAY_FLIP.
+        */
+       ret = intel_ring_cacheline_align(ring);
+       if (ret)
+               goto err_unpin;
+
        ret = intel_ring_begin(ring, len);
        if (ret)
                goto err_unpin;
-- 
1.8.3.2

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