drm/i915: protect FBC functions with FBC checks

Now all the functions called by other files check whether FBC has been
initialized. This allows us to drop the checks on the static
functions.

v2:
 - s/HAS_FBC/dev_priv->display.enable_fbc/ everywhere but the init
   function (Chris).

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_fbc.c

@@ -388,9 +388,6 @@ static void intel_fbc_enable(struct drm_crtc *crtc)
 
 	WARN_ON(!mutex_is_locked(&dev_priv->fbc.lock));
 
-	if (!dev_priv->display.enable_fbc)
-		return;
-
 	intel_fbc_cancel_work(dev_priv);
 
 	work = kzalloc(sizeof(*work), GFP_KERNEL);
@@ -430,9 +427,6 @@ static void __intel_fbc_disable(struct drm_device *dev)
 
 	intel_fbc_cancel_work(dev_priv);
 
-	if (!dev_priv->display.disable_fbc)
-		return;
-
 	dev_priv->display.disable_fbc(dev);
 	dev_priv->fbc.crtc = NULL;
 }
@@ -447,6 +441,9 @@ void intel_fbc_disable(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	if (!dev_priv->display.enable_fbc)
+		return;
+
 	mutex_lock(&dev_priv->fbc.lock);
 	__intel_fbc_disable(dev);
 	mutex_unlock(&dev_priv->fbc.lock);
@@ -463,6 +460,9 @@ void intel_fbc_disable_crtc(struct intel_crtc *crtc)
 	struct drm_device *dev = crtc->base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	if (!dev_priv->display.enable_fbc)
+		return;
+
 	mutex_lock(&dev_priv->fbc.lock);
 	if (dev_priv->fbc.crtc == crtc)
 		__intel_fbc_disable(dev);
@@ -661,6 +661,9 @@ void intel_fbc_cleanup_cfb(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	if (!dev_priv->display.enable_fbc)
+		return;
+
 	mutex_lock(&dev_priv->fbc.lock);
 	__intel_fbc_cleanup_cfb(dev);
 	mutex_unlock(&dev_priv->fbc.lock);
@@ -708,9 +711,6 @@ static void __intel_fbc_update(struct drm_device *dev)
 	const struct drm_display_mode *adjusted_mode;
 	unsigned int max_width, max_height;
 
-	if (!HAS_FBC(dev))
-		return;
-
 	WARN_ON(!mutex_is_locked(&dev_priv->fbc.lock));
 
 	/* disable framebuffer compression in vGPU */
@@ -857,6 +857,9 @@ void intel_fbc_update(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
+	if (!dev_priv->display.enable_fbc)
+		return;
+
 	mutex_lock(&dev_priv->fbc.lock);
 	__intel_fbc_update(dev);
 	mutex_unlock(&dev_priv->fbc.lock);
@@ -869,6 +872,9 @@ void intel_fbc_invalidate(struct drm_i915_private *dev_priv,
 	struct drm_device *dev = dev_priv->dev;
 	unsigned int fbc_bits;
 
+	if (!dev_priv->display.enable_fbc)
+		return;
+
 	if (origin == ORIGIN_GTT)
 		return;
 
@@ -895,6 +901,9 @@ void intel_fbc_flush(struct drm_i915_private *dev_priv,
 {
 	struct drm_device *dev = dev_priv->dev;
 
+	if (!dev_priv->display.enable_fbc)
+		return;
+
 	mutex_lock(&dev_priv->fbc.lock);
 
 	if (!dev_priv->fbc.busy_bits)