regulator: fixed: honour optionality of enable gpio

According to the binding documentation the fixed regulator enable GPIO
is optional. However so far registration thereof failed if no enable
GPIO was specified. Fix this by making it entirely optional whether an
enable GPIO is used.

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>

drivers/power/regulator/fixed.c

@@ -37,11 +37,15 @@ static int fixed_regulator_ofdata_to_platdata(struct udevice *dev)
 	/* Set type to fixed */
 	uc_pdata->type = REGULATOR_TYPE_FIXED;
 
-	/* Get fixed regulator gpio desc */
+	/* Get fixed regulator optional enable GPIO desc */
 	gpio = &dev_pdata->gpio;
 	ret = gpio_request_by_name(dev, "gpio", 0, gpio, GPIOD_IS_OUT);
-	if (ret)
-		debug("Fixed regulator gpio - not found! Error: %d", ret);
+	if (ret) {
+		debug("Fixed regulator optional enable GPIO - not found! Error: %d\n",
+		      ret);
+		if (ret != -ENOENT)
+			return ret;
+	}
 
 	/* Get optional ramp up delay */
 	dev_pdata->startup_delay_us = fdtdec_get_uint(gd->fdt_blob,
@@ -87,8 +91,9 @@ static bool fixed_regulator_get_enable(struct udevice *dev)
 {
 	struct fixed_regulator_platdata *dev_pdata = dev_get_platdata(dev);
 
+	/* Enable GPIO is optional */
 	if (!dev_pdata->gpio.dev)
-		return false;
+		return true;
 
 	return dm_gpio_get_value(&dev_pdata->gpio);
 }
@@ -98,8 +103,12 @@ static int fixed_regulator_set_enable(struct udevice *dev, bool enable)
 	struct fixed_regulator_platdata *dev_pdata = dev_get_platdata(dev);
 	int ret;
 
-	if (!dev_pdata->gpio.dev)
-		return -ENOSYS;
+	/* Enable GPIO is optional */
+	if (!dev_pdata->gpio.dev) {
+		if (!enable)
+			return -ENOSYS;
+		return 0;
+	}
 
 	ret = dm_gpio_set_value(&dev_pdata->gpio, enable);
 	if (ret) {