drm/bridge: lvds-encoder: add powerdown-gpios support

Optionally power down the LVDS-encoder when it is not in use.
Signed-off-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190111151843.11114-6-peda@axentia.se

drivers/gpu/drm/bridge/lvds-encoder.c

@@ -11,11 +11,13 @@
 #include <drm/drm_bridge.h>
 #include <drm/drm_panel.h>
 
+#include <linux/gpio/consumer.h>
 #include <linux/of_graph.h>
 
 struct lvds_encoder {
 	struct drm_bridge bridge;
 	struct drm_bridge *panel_bridge;
+	struct gpio_desc *powerdown_gpio;
 };
 
 static int lvds_encoder_attach(struct drm_bridge *bridge)
@@ -28,8 +30,30 @@ static int lvds_encoder_attach(struct drm_bridge *bridge)
 				 bridge);
 }
 
+static void lvds_encoder_enable(struct drm_bridge *bridge)
+{
+	struct lvds_encoder *lvds_encoder = container_of(bridge,
+							 struct lvds_encoder,
+							 bridge);
+
+	if (lvds_encoder->powerdown_gpio)
+		gpiod_set_value_cansleep(lvds_encoder->powerdown_gpio, 0);
+}
+
+static void lvds_encoder_disable(struct drm_bridge *bridge)
+{
+	struct lvds_encoder *lvds_encoder = container_of(bridge,
+							 struct lvds_encoder,
+							 bridge);
+
+	if (lvds_encoder->powerdown_gpio)
+		gpiod_set_value_cansleep(lvds_encoder->powerdown_gpio, 1);
+}
+
 static struct drm_bridge_funcs funcs = {
 	.attach = lvds_encoder_attach,
+	.enable = lvds_encoder_enable,
+	.disable = lvds_encoder_disable,
 };
 
 static int lvds_encoder_probe(struct platform_device *pdev)
@@ -45,6 +69,16 @@ static int lvds_encoder_probe(struct platform_device *pdev)
 	if (!lvds_encoder)
 		return -ENOMEM;
 
+	lvds_encoder->powerdown_gpio = devm_gpiod_get_optional(dev, "powerdown",
+							       GPIOD_OUT_HIGH);
+	if (IS_ERR(lvds_encoder->powerdown_gpio)) {
+		int err = PTR_ERR(lvds_encoder->powerdown_gpio);
+
+		if (err != -EPROBE_DEFER)
+			dev_err(dev, "powerdown GPIO failure: %d\n", err);
+		return err;
+	}
+
 	/* Locate the panel DT node. */
 	port = of_graph_get_port_by_id(dev->of_node, 1);
 	if (!port) {