drm/i915/fbc: Extract snb_fbc_program_fence()

We have two identical copies of the snb+ system agent
CPU fence programming code. Extract into a helper.

Also there's no real point in insisting that we
program 0 into DPFC_CPU_FENCE_OFFSET when the fence is
disabled. So just always stick the computed Y offset there
whether or not the fence is actually used or not.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211104144520.22605-2-ville.syrjala@linux.intel.comAcked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>

drivers/gpu/drm/i915/display/intel_fbc.c

@@ -307,6 +307,18 @@ static void intel_fbc_recompress(struct drm_i915_private *dev_priv)
 		i8xx_fbc_recompress(dev_priv);
 }
 
+static void snb_fbc_program_fence(struct drm_i915_private *i915)
+{
+	const struct intel_fbc_reg_params *params = &i915->fbc.params;
+	u32 ctl = 0;
+
+	if (params->fence_id >= 0)
+		ctl = SNB_CPU_FENCE_ENABLE | params->fence_id;
+
+	intel_de_write(i915, SNB_DPFC_CTL_SA, ctl);
+	intel_de_write(i915, DPFC_CPU_FENCE_OFFSET, params->fence_y_offset);
+}
+
 static void ilk_fbc_activate(struct drm_i915_private *dev_priv)
 {
 	struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
@@ -320,19 +332,11 @@ static void ilk_fbc_activate(struct drm_i915_private *dev_priv)
 		dpfc_ctl |= DPFC_CTL_FENCE_EN;
 		if (IS_IRONLAKE(dev_priv))
 			dpfc_ctl |= params->fence_id;
-		if (IS_SANDYBRIDGE(dev_priv)) {
-			intel_de_write(dev_priv, SNB_DPFC_CTL_SA,
-				       SNB_CPU_FENCE_ENABLE | params->fence_id);
-			intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET,
-				       params->fence_y_offset);
-		}
-	} else {
-		if (IS_SANDYBRIDGE(dev_priv)) {
-			intel_de_write(dev_priv, SNB_DPFC_CTL_SA, 0);
-			intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET, 0);
-		}
 	}
 
+	if (IS_SANDYBRIDGE(dev_priv))
+		snb_fbc_program_fence(dev_priv);
+
 	intel_de_write(dev_priv, ILK_DPFC_FENCE_YOFF,
 		       params->fence_y_offset);
 	/* enable it... */
@@ -389,20 +393,15 @@ static void gen7_fbc_activate(struct drm_i915_private *dev_priv)
 
 	dpfc_ctl |= g4x_dpfc_ctl_limit(dev_priv);
 
-	if (params->fence_id >= 0) {
+	if (params->fence_id >= 0)
 		dpfc_ctl |= IVB_DPFC_CTL_FENCE_EN;
-		intel_de_write(dev_priv, SNB_DPFC_CTL_SA,
-			       SNB_CPU_FENCE_ENABLE | params->fence_id);
-		intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET,
-			       params->fence_y_offset);
-	} else if (dev_priv->ggtt.num_fences) {
-		intel_de_write(dev_priv, SNB_DPFC_CTL_SA, 0);
-		intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET, 0);
-	}
 
 	if (dev_priv->fbc.false_color)
 		dpfc_ctl |= FBC_CTL_FALSE_COLOR;
 
+	if (dev_priv->ggtt.num_fences)
+		snb_fbc_program_fence(dev_priv);
+
 	intel_de_write(dev_priv, ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
 }