regulator (max5970): Add hwmon support

Utilize the integrated 10-bit ADC in Max5970/Max5978 to enable voltage
and current monitoring. This feature is seamlessly integrated through
the hwmon subsystem.
Signed-off-by: Naresh Solanki <naresh.solanki@9elements.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20231027152830.1269895-1-naresh.solanki@9elements.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/max5970-regulator.c

@@ -10,6 +10,7 @@
 #include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/err.h>
+#include <linux/hwmon.h>
 #include <linux/module.h>
 #include <linux/io.h>
 #include <linux/of.h>
@@ -32,6 +33,132 @@ enum max597x_regulator_id {
 	MAX597X_SW1,
 };
 
+static int max5970_read_adc(struct regmap *regmap, int reg, long *val)
+{
+	u8 reg_data[2];
+	int ret;
+
+	ret = regmap_bulk_read(regmap, reg, &reg_data[0], 2);
+	if (ret < 0)
+		return ret;
+
+	*val = (reg_data[0] << 2) | (reg_data[1] & 3);
+
+	return 0;
+}
+
+static int max5970_read(struct device *dev, enum hwmon_sensor_types type,
+			u32 attr, int channel, long *val)
+{
+	struct regulator_dev **rdevs = dev_get_drvdata(dev);
+	struct max5970_regulator *ddata = rdev_get_drvdata(rdevs[channel]);
+	struct regmap *regmap = ddata->regmap;
+	int ret;
+
+	switch (type) {
+	case hwmon_curr:
+		switch (attr) {
+		case hwmon_curr_input:
+			ret = max5970_read_adc(regmap, MAX5970_REG_CURRENT_H(channel), val);
+			if (ret < 0)
+				return ret;
+			/*
+			 * Calculate current from ADC value, IRNG range & shunt resistor value.
+			 * ddata->irng holds the voltage corresponding to the maximum value the
+			 * 10-bit ADC can measure.
+			 * To obtain the output, multiply the ADC value by the IRNG range (in
+			 * millivolts) and then divide it by the maximum value of the 10-bit ADC.
+			 */
+			*val = (*val * ddata->irng) >> 10;
+			/* Convert the voltage meansurement across shunt resistor to current */
+			*val = (*val * 1000) / ddata->shunt_micro_ohms;
+			return 0;
+		default:
+			return -EOPNOTSUPP;
+		}
+
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_input:
+			ret = max5970_read_adc(regmap, MAX5970_REG_VOLTAGE_H(channel), val);
+			if (ret < 0)
+				return ret;
+			/*
+			 * Calculate voltage from ADC value and MON range.
+			 * ddata->mon_rng holds the voltage corresponding to the maximum value the
+			 * 10-bit ADC can measure.
+			 * To obtain the output, multiply the ADC value by the MON range (in
+			 * microvolts) and then divide it by the maximum value of the 10-bit ADC.
+			 */
+			*val = mul_u64_u32_shr(*val, ddata->mon_rng, 10);
+			/* uV to mV */
+			*val = *val / 1000;
+			return 0;
+		default:
+			return -EOPNOTSUPP;
+		}
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static umode_t max5970_is_visible(const void *data,
+				  enum hwmon_sensor_types type,
+				  u32 attr, int channel)
+{
+	struct regulator_dev **rdevs = (struct regulator_dev **)data;
+	struct max5970_regulator *ddata;
+
+	if (channel >= MAX5970_NUM_SWITCHES || !rdevs[channel])
+		return 0;
+
+	ddata = rdev_get_drvdata(rdevs[channel]);
+
+	if (channel >= ddata->num_switches)
+		return 0;
+
+	switch (type) {
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_input:
+			return 0444;
+		default:
+			break;
+		}
+		break;
+	case hwmon_curr:
+		switch (attr) {
+		case hwmon_curr_input:
+			/* Current measurement requires knowledge of the shunt resistor value. */
+			if (ddata->shunt_micro_ohms)
+				return 0444;
+			break;
+		default:
+			break;
+		}
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
+static const struct hwmon_ops max5970_hwmon_ops = {
+	.is_visible = max5970_is_visible,
+	.read = max5970_read,
+};
+
+static const struct hwmon_channel_info *max5970_info[] = {
+	HWMON_CHANNEL_INFO(in, HWMON_I_INPUT, HWMON_I_INPUT),
+	HWMON_CHANNEL_INFO(curr, HWMON_C_INPUT, HWMON_C_INPUT),
+	NULL
+};
+
+static const struct hwmon_chip_info max5970_chip_info = {
+	.ops = &max5970_hwmon_ops,
+	.info = max5970_info,
+};
+
 static int max597x_uvp_ovp_check_mode(struct regulator_dev *rdev, int severity)
 {
 	int ret, reg;
@@ -431,7 +558,8 @@ static int max597x_regulator_probe(struct platform_device *pdev)
 	struct i2c_client *i2c = to_i2c_client(pdev->dev.parent);
 	struct regulator_config config = { };
 	struct regulator_dev *rdev;
-	struct regulator_dev *rdevs[MAX5970_NUM_SWITCHES];
+	struct regulator_dev **rdevs = NULL;
+	struct device *hwmon_dev;
 	int num_switches;
 	int ret, i;
 
@@ -442,6 +570,11 @@ static int max597x_regulator_probe(struct platform_device *pdev)
 	if (!max597x)
 		return -ENOMEM;
 
+	rdevs = devm_kcalloc(&i2c->dev, MAX5970_NUM_SWITCHES, sizeof(struct regulator_dev *),
+			     GFP_KERNEL);
+	if (!rdevs)
+		return -ENOMEM;
+
 	i2c_set_clientdata(i2c, max597x);
 
 	if (of_device_is_compatible(i2c->dev.of_node, "maxim,max5978"))
@@ -485,6 +618,15 @@ static int max597x_regulator_probe(struct platform_device *pdev)
 		max597x->shunt_micro_ohms[i] = data->shunt_micro_ohms;
 	}
 
+	if (IS_REACHABLE(CONFIG_HWMON)) {
+		hwmon_dev = devm_hwmon_device_register_with_info(&i2c->dev, "max5970", rdevs,
+								 &max5970_chip_info, NULL);
+		if (IS_ERR(hwmon_dev)) {
+			return dev_err_probe(&i2c->dev, PTR_ERR(hwmon_dev),
+					     "Unable to register hwmon device\n");
+		}
+	}
+
 	if (i2c->irq) {
 		ret =
 		    max597x_setup_irq(&i2c->dev, i2c->irq, rdevs, num_switches,