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

Gen2 and gen3 require fences for tiled scanout, but gen4+ only require a
fence for FBC GTT modification tracking. Install a fence for scanout
only when it might actually be required.

This could potentially be optimized even further, but this seems like
a fair comporomise for now.

Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index fd48c2e..71dd041 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1972,6 +1972,13 @@ int intel_pin_fenced_fb_obj(struct drm_device *dev,
        u32 alignment;
        int ret;
 
+       /*
+        * Pre-i965 always needs a fence for tiled scanout, whereas
+        * 965+ only requires a fence if using framebuffer compression.
+        */
+       if (INTEL_INFO(dev)->gen >= 4 && !HAS_FBC(dev))
+               return intel_pin_fb_obj(dev, obj, pipelined);
+
        ret = intel_fb_obj_alignment(dev, obj, &alignment);
        if (ret)
                return ret;
@@ -1981,11 +1988,6 @@ int intel_pin_fenced_fb_obj(struct drm_device *dev,
        if (ret)
                goto err_interruptible;
 
-       /* Install a fence for tiled scan-out. Pre-i965 always needs a
-        * fence, whereas 965+ only requires a fence if using
-        * framebuffer compression.  For simplicity, we always install
-        * a fence as the cost is not that onerous.
-        */
        ret = i915_gem_object_get_fence(obj);
        if (ret)
                goto err_unpin;
@@ -2004,6 +2006,13 @@ err_interruptible:
 
 void intel_unpin_fenced_fb_obj(struct drm_i915_gem_object *obj)
 {
+       struct drm_device *dev = obj->base.dev;
+
+       if (INTEL_INFO(dev)->gen >= 4 && !HAS_FBC(dev)) {
+               intel_unpin_fb_obj(obj);
+               return;
+       }
+
        i915_gem_object_unpin_fence(obj);
        i915_gem_object_unpin_from_display_plane(obj);
 }
-- 
1.8.3.2

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