drm/i915: Don't set the fence number in DPFC_CTL on SNB

SNB has another register where the actual FBC CPU fence number is
stored. The documenation explicitly states that the fence number
in DPFC_CTL must be 0 on SNB. And in fact when it's not zero,
the GTT tracking simply doesn't work.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 0fcd591b0a4b..de4cf565ec4c 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -222,7 +222,9 @@ static void ironlake_enable_fbc(struct drm_crtc *crtc, unsigned long interval)
         dpfc_ctl |= (plane | DPFC_CTL_LIMIT_1X);
         /* Set persistent mode for front-buffer rendering, ala X. */
         dpfc_ctl |= DPFC_CTL_PERSISTENT_MODE;
-        dpfc_ctl |= (DPFC_CTL_FENCE_EN | obj->fence_reg);
+        dpfc_ctl |= DPFC_CTL_FENCE_EN;
+        if (IS_GEN5(dev))
+                dpfc_ctl |= obj->fence_reg;
         I915_WRITE(ILK_DPFC_CHICKEN, DPFC_HT_MODIFY);
 
         I915_WRITE(ILK_DPFC_RECOMP_CTL, DPFC_RECOMP_STALL_EN |