regulator: new API for voltage reference supplies

Merge series from David Lechner <dlechner@baylibre.com>:

In the IIO subsystem, we noticed a pattern in many drivers where we need
to get, enable and get the voltage of a supply that provides a reference
voltage. In these cases, we only need the voltage and not a handle to
the regulator. Another common pattern is for chips to have an internal
reference voltage that is used when an external reference is not
available. There are also a few drivers outside of IIO that do the same.

So we would like to propose a new regulator consumer API to handle these
specific cases to avoid repeating the same boilerplate code in multiple
drivers.

As an example of how these functions are used, I have included a few
patches to consumer drivers. But to avoid a giant patch bomb, I have
omitted the iio/adc and iio/dac patches I have prepared from this
series. I will send those separately but these will add 36 more users
of devm_regulator_get_enable_read_voltage() in addition to the 6 here.
In total, this will eliminate nearly 1000 lines of similar code and will
simplify writing and reviewing new drivers in the future.

2 files changed, 66 insertions, 0 deletions

diff --git a/drivers/regulator/devres.c b/drivers/regulator/devres.c
index 90bb0d178885..4f290b9b559b 100644
--- a/drivers/regulator/devres.c
+++ b/drivers/regulator/devres.c
@@ -145,6 +145,65 @@ struct regulator *devm_regulator_get_optional(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_regulator_get_optional);
 
+/**
+ * devm_regulator_get_enable_read_voltage - Resource managed regulator get and
+ *                                          enable that returns the voltage
+ * @dev: device to supply
+ * @id:  supply name or regulator ID.
+ *
+ * Get and enable regulator for duration of the device life-time.
+ * regulator_disable() and regulator_put() are automatically called on driver
+ * detach. See regulator_get_optional(), regulator_enable(), and
+ * regulator_get_voltage() for more information.
+ *
+ * This is a convenience function for supplies that provide a reference voltage
+ * where the consumer driver just needs to know the voltage and keep the
+ * regulator enabled.
+ *
+ * In cases where the supply is not strictly required, callers can check for
+ * -ENODEV error and handle it accordingly.
+ *
+ * Returns: voltage in microvolts on success, or an error code on failure.
+ */
+int devm_regulator_get_enable_read_voltage(struct device *dev, const char *id)
+{
+	struct regulator *r;
+	int ret;
+
+	/*
+	 * Since we need a real voltage, we use devm_regulator_get_optional()
+	 * rather than getting a dummy regulator with devm_regulator_get() and
+	 * then letting regulator_get_voltage() fail with -EINVAL. This way, the
+	 * caller can handle the -ENODEV error code if needed instead of the
+	 * ambiguous -EINVAL.
+	 */
+	r = devm_regulator_get_optional(dev, id);
+	if (IS_ERR(r))
+		return PTR_ERR(r);
+
+	ret = regulator_enable(r);
+	if (ret)
+		goto err_regulator_put;
+
+	ret = devm_add_action_or_reset(dev, regulator_action_disable, r);
+	if (ret)
+		goto err_regulator_put;
+
+	ret = regulator_get_voltage(r);
+	if (ret < 0)
+		goto err_release_action;
+
+	return 0;
+
+err_release_action:
+	devm_release_action(dev, regulator_action_disable, r);
+err_regulator_put:
+	devm_regulator_put(r);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(devm_regulator_get_enable_read_voltage);
+
 static int devm_regulator_match(struct device *dev, void *res, void *data)
 {
 	struct regulator **r = res;
diff --git a/drivers/regulator/tps65132-regulator.c b/drivers/regulator/tps65132-regulator.c
index a06f5f2d7932..9c2f0dd42613 100644
--- a/drivers/regulator/tps65132-regulator.c
+++ b/drivers/regulator/tps65132-regulator.c
@@ -267,10 +267,17 @@ static const struct i2c_device_id tps65132_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, tps65132_id);
 
+static const struct of_device_id __maybe_unused tps65132_of_match[] = {
+	{ .compatible = "ti,tps65132" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, tps65132_of_match);
+
 static struct i2c_driver tps65132_i2c_driver = {
 	.driver = {
 		.name = "tps65132",
 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = of_match_ptr(tps65132_of_match),
 	},
 	.probe = tps65132_probe,
 	.id_table = tps65132_id,