i2c: pca954x: Add reset GPIO support

If a reset GPIO support is specified, request the GPIO and get the chip
out of reset at probe time.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt

@@ -13,6 +13,10 @@ Required Properties:
   - Standard I2C mux properties. See i2c-mux.txt in this directory.
   - I2C child bus nodes. See i2c-mux.txt in this directory.
 
+Optional Properties:
+
+  - reset-gpios: Reference to the GPIO connected to the reset input.
+
 
 Example:
 

drivers/i2c/muxes/i2c-mux-pca954x.c

@@ -36,11 +36,13 @@
  */
 
 #include <linux/device.h>
+#include <linux/gpio.h>
 #include <linux/i2c.h>
 #include <linux/i2c-mux.h>
 #include <linux/i2c/pca954x.h>
 #include <linux/init.h>
 #include <linux/module.h>
+#include <linux/of_gpio.h>
 #include <linux/slab.h>
 
 #define PCA954X_MAX_NCHANS 8
@@ -185,6 +187,7 @@ static int pca954x_probe(struct i2c_client *client,
 {
 	struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
 	struct pca954x_platform_data *pdata = dev_get_platdata(&client->dev);
+	struct device_node *np = client->dev.of_node;
 	int num, force, class;
 	struct pca954x *data;
 	int ret;
@@ -198,6 +201,22 @@ static int pca954x_probe(struct i2c_client *client,
 
 	i2c_set_clientdata(client, data);
 
+	if (IS_ENABLED(CONFIG_OF) && np) {
+		enum of_gpio_flags flags;
+		int gpio;
+
+		/* Get the mux out of reset if a reset GPIO is specified. */
+		gpio = of_get_named_gpio_flags(np, "reset-gpio", 0, &flags);
+		if (gpio_is_valid(gpio)) {
+			ret = devm_gpio_request_one(&client->dev, gpio,
+					flags & OF_GPIO_ACTIVE_LOW ?
+					GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW,
+					"pca954x reset");
+			if (ret < 0)
+				return ret;
+		}
+	}
+
 	/* Write the mux register at addr to verify
 	 * that the mux is in fact present. This also
 	 * initializes the mux to disconnected state.