Re: [PATCH] regulator (max5970): Add hwmon support

[Guenter Roeck]

On 8/30/23 04:13, Naresh Solanki wrote:
> 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@xxxxxxxxxxxxx>
> ---
>   drivers/regulator/max5970-regulator.c | 119 ++++++++++++++++++++++++++
>   1 file changed, 119 insertions(+)
>
> diff --git a/drivers/regulator/max5970-regulator.c b/drivers/regulator/max5970-regulator.c
> index b56a174cde3d..3a6f7c293526 100644
> --- a/drivers/regulator/max5970-regulator.c
> +++ b/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 +33,116 @@ 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 max5970_data *ddata = dev_get_drvdata(dev);
> +	struct regmap *regmap = dev_get_regmap(dev->parent, NULL);
> +	int ret;
> +
> +	switch (type) {
> +	case hwmon_curr:
> +		switch (attr) {
> +		case hwmon_curr_input:
> +			ret = max5970_read_adc(regmap, MAX5970_REG_CURRENT_H(channel), val);
> +			/*
> +			 * 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[channel]) >> 10;
> +			/* Convert the voltage meansurement across shunt resistor to current */
> +			*val = (*val * 1000) / ddata->shunt_micro_ohms[channel];
> +			return ret;
> +		default:
> +			return -EOPNOTSUPP;
> +		}
> +
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_input:
> +			ret = max5970_read_adc(regmap, MAX5970_REG_VOLTAGE_H(channel), val);
> +			/*
> +			 * 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[channel], 10);

Why do you use mul_u64_u32_shr() here but a direct shift above ?

> +			/* uV to mV */
> +			*val = *val / 1000;
> +			return ret;
> +		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 max5970_data *ddata = (struct max5970_data *)data;
> +
> +	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[channel])
> +				return 0444;
		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),

Your call, but the chip does support limit and status registers, so you
could add reporting those as well since you are at it, possibly even including
notifications.

> +	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;
> @@ -432,6 +543,7 @@ static int max597x_regulator_probe(struct platform_device *pdev)
>   	struct regulator_config config = { };
>   	struct regulator_dev *rdev;
>   	struct regulator_dev *rdevs[MAX5970_NUM_SWITCHES];
> +	struct device *hwmon_dev;
>   	int num_switches;
>   	int ret, i;
>   
> @@ -485,6 +597,13 @@ static int max597x_regulator_probe(struct platform_device *pdev)
>   		max597x->shunt_micro_ohms[i] = data->shunt_micro_ohms;
>   	}
>   
> +	hwmon_dev = devm_hwmon_device_register_with_info(&i2c->dev, "max5970_hwmon", max597x,
> +							 &max5970_chip_info, NULL);

This makes the driver dependent on hwmon, so you either need a strict
	depends on HWMON
in Kconfig, or
	depends on HWMON || HWMON=n
and add #if IS_ENABLED(CONFIG_HWMON) as appropriate into the code.


> +	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,
>
> base-commit: 35d0d2350d774fecf596cfb2fb050559fe5e1850