drm/i915: Handle changing enable_fbc parameter at runtime better.

If i915.enable_fbc is cleared at runtime, but FBC was previously enabled
then we don't disable FBC until the next time the crtc is disabled.

Make sure that if the module param is changed, we disable FBC in
intel_fbc_post_update so we never have to worry about disabling.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180305123608.20665-1-maarten.lankhorst@linux.intel.comReviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/intel_fbc.c

@@ -960,6 +960,30 @@ void intel_fbc_pre_update(struct intel_crtc *crtc,
 	mutex_unlock(&fbc->lock);
 }
 
+/**
+ * __intel_fbc_disable - disable FBC
+ * @dev_priv: i915 device instance
+ *
+ * This is the low level function that actually disables FBC. Callers should
+ * grab the FBC lock.
+ */
+static void __intel_fbc_disable(struct drm_i915_private *dev_priv)
+{
+	struct intel_fbc *fbc = &dev_priv->fbc;
+	struct intel_crtc *crtc = fbc->crtc;
+
+	WARN_ON(!mutex_is_locked(&fbc->lock));
+	WARN_ON(!fbc->enabled);
+	WARN_ON(fbc->active);
+
+	DRM_DEBUG_KMS("Disabling FBC on pipe %c\n", pipe_name(crtc->pipe));
+
+	__intel_fbc_cleanup_cfb(dev_priv);
+
+	fbc->enabled = false;
+	fbc->crtc = NULL;
+}
+
 static void __intel_fbc_post_update(struct intel_crtc *crtc)
 {
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
@@ -971,6 +995,13 @@ static void __intel_fbc_post_update(struct intel_crtc *crtc)
 	if (!fbc->enabled || fbc->crtc != crtc)
 		return;
 
+	if (!i915_modparams.enable_fbc) {
+		intel_fbc_deactivate(dev_priv, "disabled at runtime per module param");
+		__intel_fbc_disable(dev_priv);
+
+		return;
+	}
+
 	if (!intel_fbc_can_activate(crtc)) {
 		WARN_ON(fbc->active);
 		return;
@@ -1174,31 +1205,6 @@ void intel_fbc_enable(struct intel_crtc *crtc,
 	mutex_unlock(&fbc->lock);
 }
 
-/**
- * __intel_fbc_disable - disable FBC
- * @dev_priv: i915 device instance
- *
- * This is the low level function that actually disables FBC. Callers should
- * grab the FBC lock.
- */
-static void __intel_fbc_disable(struct drm_i915_private *dev_priv)
-{
-	struct intel_fbc *fbc = &dev_priv->fbc;
-	struct intel_crtc *crtc = fbc->crtc;
-
-	WARN_ON(!mutex_is_locked(&fbc->lock));
-	WARN_ON(!fbc->enabled);
-	WARN_ON(fbc->active);
-	WARN_ON(crtc->active);
-
-	DRM_DEBUG_KMS("Disabling FBC on pipe %c\n", pipe_name(crtc->pipe));
-
-	__intel_fbc_cleanup_cfb(dev_priv);
-
-	fbc->enabled = false;
-	fbc->crtc = NULL;
-}
-
 /**
  * intel_fbc_disable - disable FBC if it's associated with crtc
  * @crtc: the CRTC
@@ -1213,6 +1219,8 @@ void intel_fbc_disable(struct intel_crtc *crtc)
 	if (!fbc_supported(dev_priv))
 		return;
 
+	WARN_ON(crtc->active);
+
 	mutex_lock(&fbc->lock);
 	if (fbc->crtc == crtc)
 		__intel_fbc_disable(dev_priv);
@@ -1235,8 +1243,10 @@ void intel_fbc_global_disable(struct drm_i915_private *dev_priv)
 		return;
 
 	mutex_lock(&fbc->lock);
-	if (fbc->enabled)
+	if (fbc->enabled) {
+		WARN_ON(fbc->crtc->active);
 		__intel_fbc_disable(dev_priv);
+	}
 	mutex_unlock(&fbc->lock);
 
 	cancel_work_sync(&fbc->work.work);