This chicken bit should be set before enabling FBC to avoid screen
corruption when the plane size has odd vertical and horizontal
dimensions.  It is safe to leave the bit set even when FBC is disabled.

v2:
 - The bspec's name for this bit on these platforms ("Spare 14") is
   pretty meaningless.  Let's rename the bit definition to something
   that more accurately reflects what the bit really does.  (Clint)

Cc: Clinton Taylor <clinton.a.tay...@intel.com>
Signed-off-by: Matt Roper <matthew.d.ro...@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h  | 2 ++
 drivers/gpu/drm/i915/intel_fbc.c | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index edf9f93934a1..54654a578c84 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3150,6 +3150,8 @@ enum i915_power_well_id {
 
 /* Framebuffer compression for Ironlake */
 #define ILK_DPFC_CB_BASE       _MMIO(0x43200)
+#define ILK_DPFC_CHICKEN       _MMIO(0x43224)
+#define   ILK_DPFC_CHICKEN_COMP_DUMMY_PIXEL    REG_BIT(14)
 #define ILK_DPFC_CONTROL       _MMIO(0x43208)
 #define   FBC_CTL_FALSE_COLOR  (1 << 10)
 /* The bit 28-8 is reserved */
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index 5679f2fffb7c..d36cada2cc7d 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -344,6 +344,10 @@ static void gen7_fbc_activate(struct drm_i915_private 
*dev_priv)
                           HSW_FBCQ_DIS);
        }
 
+       if (IS_GEN(dev_priv, 11))
+               /* Wa_1409120013:icl,ehl */
+               I915_WRITE(ILK_DPFC_CHICKEN, ILK_DPFC_CHICKEN_COMP_DUMMY_PIXEL);
+
        I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
 
        intel_fbc_recompress(dev_priv);
-- 
2.14.5

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