drm/tegra: rgb: Fix the unbound reference count

The of_get_child_by_name() increments the refcount in tegra_dc_rgb_probe,
but the driver does not decrement the refcount during unbind. Fix the
unbound reference count using devm_add_action_or_reset() helper.

Fixes: d8f4a9e ("drm: Add NVIDIA Tegra20 support")
Signed-off-by: Biju Das <[email protected]>
Signed-off-by: Thierry Reding <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: bijudas

drivers/gpu/drm/tegra/rgb.c

@@ -200,14 +200,26 @@ static const struct drm_encoder_helper_funcs tegra_rgb_encoder_helper_funcs = {
 	.atomic_check = tegra_rgb_encoder_atomic_check,
 };
 
+static void tegra_dc_of_node_put(void *data)
+{
+	of_node_put(data);
+}
+
 int tegra_dc_rgb_probe(struct tegra_dc *dc)
 {
 	struct device_node *np;
 	struct tegra_rgb *rgb;
 	int err;
 
 	np = of_get_child_by_name(dc->dev->of_node, "rgb");
-	if (!np || !of_device_is_available(np))
+	if (!np)
+		return -ENODEV;
+
+	err = devm_add_action_or_reset(dc->dev, tegra_dc_of_node_put, np);
+	if (err < 0)
+		return err;
+
+	if (!of_device_is_available(np))
 		return -ENODEV;
 
 	rgb = devm_kzalloc(dc->dev, sizeof(*rgb), GFP_KERNEL);