drm/bridge: simple-bridge: Add support for enable GPIO

If an enable GPIO is declared in the firmware, assert it when enabling
the bridge and deassert it when disabling it.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200226112514.12455-14-laurent.pinchart@ideasonboard.com

drivers/gpu/drm/bridge/simple-bridge.c

@@ -6,6 +6,7 @@
  * Maxime Ripard <maxime.ripard@free-electrons.com>
  */
 
+#include <linux/gpio/consumer.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/of_graph.h>
@@ -30,6 +31,7 @@ struct simple_bridge {
 
 	struct i2c_adapter	*ddc;
 	struct regulator	*vdd;
+	struct gpio_desc	*enable;
 };
 
 static inline struct simple_bridge *
@@ -143,19 +145,23 @@ static int simple_bridge_attach(struct drm_bridge *bridge,
 static void simple_bridge_enable(struct drm_bridge *bridge)
 {
 	struct simple_bridge *sbridge = drm_bridge_to_simple_bridge(bridge);
-	int ret = 0;
+	int ret;
 
-	if (sbridge->vdd)
+	if (sbridge->vdd) {
 		ret = regulator_enable(sbridge->vdd);
-
 		if (ret)
 			DRM_ERROR("Failed to enable vdd regulator: %d\n", ret);
+	}
+
+	gpiod_set_value_cansleep(sbridge->enable, 1);
 }
 
 static void simple_bridge_disable(struct drm_bridge *bridge)
 {
 	struct simple_bridge *sbridge = drm_bridge_to_simple_bridge(bridge);
 
+	gpiod_set_value_cansleep(sbridge->enable, 0);
+
 	if (sbridge->vdd)
 		regulator_disable(sbridge->vdd);
 }
@@ -208,6 +214,14 @@ static int simple_bridge_probe(struct platform_device *pdev)
 		dev_dbg(&pdev->dev, "No vdd regulator found: %d\n", ret);
 	}
 
+	sbridge->enable = devm_gpiod_get_optional(&pdev->dev, "enable",
+						  GPIOD_OUT_LOW);
+	if (IS_ERR(sbridge->enable)) {
+		if (PTR_ERR(sbridge->enable) != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "Unable to retrieve enable GPIO\n");
+		return PTR_ERR(sbridge->enable);
+	}
+
 	sbridge->ddc = simple_bridge_retrieve_ddc(&pdev->dev);
 	if (IS_ERR(sbridge->ddc)) {
 		if (PTR_ERR(sbridge->ddc) == -ENODEV) {