i2c-mux-pca954x: Add regulator support

Add an optional vcc regulator and enable it when found for devices
that are powered off by default.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>

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

@@ -48,6 +48,7 @@
 #include <linux/module.h>
 #include <linux/pm.h>
 #include <linux/property.h>
+#include <linux/regulator/consumer.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <dt-bindings/mux/mux.h>
@@ -101,6 +102,7 @@ struct pca954x {
 	struct irq_domain *irq;
 	unsigned int irq_mask;
 	raw_spinlock_t lock;
+	struct regulator *supply;
 };
 
 /* Provide specs for the PCA954x and MAX735x types we know about */
@@ -425,6 +427,9 @@ static void pca954x_cleanup(struct i2c_mux_core *muxc)
 	struct pca954x *data = i2c_mux_priv(muxc);
 	int c, irq;
 
+	if (!IS_ERR_OR_NULL(data->supply))
+		regulator_disable(data->supply);
+
 	if (data->irq) {
 		for (c = 0; c < data->chip->nchans; c++) {
 			irq = irq_find_mapping(data->irq, c);
@@ -484,15 +489,31 @@ static int pca954x_probe(struct i2c_client *client,
 			     pca954x_select_chan, pca954x_deselect_mux);
 	if (!muxc)
 		return -ENOMEM;
+
 	data = i2c_mux_priv(muxc);
 
 	i2c_set_clientdata(client, muxc);
 	data->client = client;
 
+	data->supply = devm_regulator_get(dev, "vcc");
+	if (IS_ERR(data->supply)) {
+		if ((PTR_ERR(data->supply) == -EPROBE_DEFER))
+			return -EPROBE_DEFER;
+		dev_warn(dev, "Failed to get regulator for vcc: %d\n", ret);
+	} else {
+		ret = regulator_enable(data->supply);
+		if (ret) {
+			dev_err(dev, "Failed to enable regulator vcc\n");
+			return ret;
+		}
+	}
+
 	/* Reset the mux if a reset GPIO is specified. */
 	gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
-	if (IS_ERR(gpio))
-		return PTR_ERR(gpio);
+	if (IS_ERR(gpio)) {
+		ret = PTR_ERR(gpio);
+		goto fail_cleanup;
+	}
 	if (gpio) {
 		udelay(1);
 		gpiod_set_value_cansleep(gpio, 0);
@@ -509,15 +530,16 @@ static int pca954x_probe(struct i2c_client *client,
 
 		ret = i2c_get_device_id(client, &id);
 		if (ret && ret != -EOPNOTSUPP)
-			return ret;
+			goto fail_cleanup;
 
 		if (!ret &&
 		    (id.manufacturer_id != data->chip->id.manufacturer_id ||
 		     id.part_id != data->chip->id.part_id)) {
 			dev_warn(dev, "unexpected device id %03x-%03x-%x\n",
 				 id.manufacturer_id, id.part_id,
 				 id.die_revision);
-			return -ENODEV;
+			ret = -ENODEV;
+			goto fail_cleanup;
 		}
 	}
 
@@ -536,7 +558,8 @@ static int pca954x_probe(struct i2c_client *client,
 	ret = pca954x_init(client, data);
 	if (ret < 0) {
 		dev_warn(dev, "probe failed\n");
-		return -ENODEV;
+		ret = -ENODEV;
+		goto fail_cleanup;
 	}
 
 	ret = pca954x_irq_setup(muxc);