drm/i915: only set TV mode when any property changed

If there's no real property change, don't need to set TV mode again.
Signed-off-by: NZhenyu Wang <zhenyu.z.wang@intel.com>
[anholt: checkpatch.pl fix]
Signed-off-by: NEric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_tv.c

@@ -1571,32 +1571,45 @@ intel_tv_set_property(struct drm_connector *connector, struct drm_property *prop
 	struct intel_output *intel_output = to_intel_output(connector);
 	struct intel_tv_priv *tv_priv = intel_output->dev_priv;
 	int ret = 0;
+	bool changed = false;
 
 	ret = drm_connector_property_set_value(connector, property, val);
 	if (ret < 0)
 		goto out;
 
-	if (property == dev->mode_config.tv_left_margin_property)
+	if (property == dev->mode_config.tv_left_margin_property &&
+		tv_priv->margin[TV_MARGIN_LEFT] != val) {
 		tv_priv->margin[TV_MARGIN_LEFT] = val;
-	else if (property == dev->mode_config.tv_right_margin_property)
+		changed = true;
+	} else if (property == dev->mode_config.tv_right_margin_property &&
+		tv_priv->margin[TV_MARGIN_RIGHT] != val) {
 		tv_priv->margin[TV_MARGIN_RIGHT] = val;
-	else if (property == dev->mode_config.tv_top_margin_property)
+		changed = true;
+	} else if (property == dev->mode_config.tv_top_margin_property &&
+		tv_priv->margin[TV_MARGIN_TOP] != val) {
 		tv_priv->margin[TV_MARGIN_TOP] = val;
-	else if (property == dev->mode_config.tv_bottom_margin_property)
+		changed = true;
+	} else if (property == dev->mode_config.tv_bottom_margin_property &&
+		tv_priv->margin[TV_MARGIN_BOTTOM] != val) {
 		tv_priv->margin[TV_MARGIN_BOTTOM] = val;
-	else if (property == dev->mode_config.tv_mode_property) {
+		changed = true;
+	} else if (property == dev->mode_config.tv_mode_property) {
 		if (val >= NUM_TV_MODES) {
 			ret = -EINVAL;
 			goto out;
 		}
+		if (!strcmp(tv_priv->tv_format, tv_modes[val].name))
+			goto out;
+
 		tv_priv->tv_format = tv_modes[val].name;
-		intel_tv_mode_set(&intel_output->enc, NULL, NULL);
+		changed = true;
 	} else {
 		ret = -EINVAL;
 		goto out;
 	}
 
-	intel_tv_mode_set(&intel_output->enc, NULL, NULL);
+	if (changed)
+		intel_tv_mode_set(&intel_output->enc, NULL, NULL);
 out:
 	return ret;
 }