Commit b11f3d47 authored by John Pruitt's avatar John Pruitt Committed by Guenter Roeck
Browse files

hwmon: (ltc2945) Allow setting shunt resistor 



Add the ability to specify the value of the shunt resistor in the
device tree instead of assuming it is 1 milliOhm. The value in the
device tree has the name shunt-resistor-micro-ohms and the
default value is 1000 micro-ohms in order to preserve the
current behavior.

Signed-off-by: default avatarJonathan Cormier <jcormier@criticallink.com>
Signed-off-by: default avatarJohn Pruitt <jpruitt@criticallink.com>
[groeck: Fixed multi-line alignment, squashed last patch of series]
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 178b01ec

drivers/hwmon/ltc2945.c

+76 −43
Original line number Diff line number Diff line
@@ -64,6 +64,16 @@ static const struct of_device_id __maybe_unused ltc2945_of_match[] = { 
};

MODULE_DEVICE_TABLE(of, ltc2945_of_match);



/**

 * struct ltc2945_data - LTC2945 device data

 * @regmap: regmap device

 * @shunt_resistor: shunt resistor value in micro ohms (1000 by default)

 */

struct ltc2945_data {

	struct regmap *regmap;

	u32 shunt_resistor;

};



static inline bool is_power_reg(u8 reg)

{

	return reg < LTC2945_SENSE_H;
@@ -72,7 +82,9 @@ static inline bool is_power_reg(u8 reg) 
/* Return the value from the given register in uW, mV, or mA */

static long long ltc2945_reg_to_val(struct device *dev, u8 reg)

{

	struct regmap *regmap = dev_get_drvdata(dev);

	struct ltc2945_data *data = dev_get_drvdata(dev);

	struct regmap *regmap = data->regmap;

	u32 shunt_resistor = data->shunt_resistor;

	unsigned int control;

	u8 buf[3];

	long long val;
@@ -84,10 +96,10 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) 
		return ret;



	if (is_power_reg(reg)) {

		/* power */

		/* 24-bit power */

		val = (buf[0] << 16) + (buf[1] << 8) + buf[2];

	} else {

		/* current, voltage */

		/* 12-bit current, voltage */

		val = (buf[0] << 4) + (buf[1] >> 4);

	}
@@ -98,9 +110,7 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) 
	case LTC2945_MAX_POWER_THRES_H:

	case LTC2945_MIN_POWER_THRES_H:

		/*

		 * Convert to uW by assuming current is measured with

		 * an 1mOhm sense resistor, similar to current

		 * measurements.

		 * Convert to uW

		 * Control register bit 0 selects if voltage at SENSE+/VDD

		 * or voltage at ADIN is used to measure power.

		 */
@@ -114,6 +124,14 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) 
			/* 0.5 mV * 25 uV = 0.0125 uV resolution. */

			val = (val * 25LL) >> 1;

		}

		val *= 1000;

		/* Overflow check: Assuming max 24-bit power, val is at most 53 bits right now. */

		val = DIV_ROUND_CLOSEST_ULL(val, shunt_resistor);

		/*

		 * Overflow check: After division, depending on shunt resistor,

		 * val can still be > 32 bits so returning long long makes sense

		 */



		break;

	case LTC2945_VIN_H:

	case LTC2945_MAX_VIN_H:
@@ -136,14 +154,11 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) 
	case LTC2945_MIN_SENSE_H:

	case LTC2945_MAX_SENSE_THRES_H:

	case LTC2945_MIN_SENSE_THRES_H:

		/*

		 * 25 uV resolution. Convert to current as measured with

		 * an 1 mOhm sense resistor, in mA. If a different sense

		 * resistor is installed, calculate the actual current by

		 * dividing the reported current by the sense resistor value

		 * in mOhm.

		 */

		val *= 25;

		/* 25 uV resolution. Convert to mA. */

		val *= 25 * 1000;

		/* Overflow check: Assuming max 12-bit sense, val is at most 27 bits right now */

		val = DIV_ROUND_CLOSEST_ULL(val, shunt_resistor);

		/* Overflow check: After division, <= 27 bits */

		break;

	default:

		return -EINVAL;
@@ -151,13 +166,18 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) 
	return val;

}



static int ltc2945_val_to_reg(struct device *dev, u8 reg,

			      unsigned long val)

static long long ltc2945_val_to_reg(struct device *dev, u8 reg,

				    unsigned long long val)

{

	struct regmap *regmap = dev_get_drvdata(dev);

	struct ltc2945_data *data = dev_get_drvdata(dev);

	struct regmap *regmap = data->regmap;

	u32 shunt_resistor = data->shunt_resistor;

	unsigned int control;

	int ret;



	/* Ensure we don't overflow */

	val = clamp_val(val, 0, U32_MAX);



	switch (reg) {

	case LTC2945_POWER_H:

	case LTC2945_MAX_POWER_H:
@@ -165,9 +185,6 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, 
	case LTC2945_MAX_POWER_THRES_H:

	case LTC2945_MIN_POWER_THRES_H:

		/*

		 * Convert to register value by assuming current is measured

		 * with an 1mOhm sense resistor, similar to current

		 * measurements.

		 * Control register bit 0 selects if voltage at SENSE+/VDD

		 * or voltage at ADIN is used to measure power, which in turn

		 * determines register calculations.
@@ -177,14 +194,16 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, 
			return ret;

		if (control & CONTROL_MULT_SELECT) {

			/* 25 mV * 25 uV = 0.625 uV resolution. */

			val = DIV_ROUND_CLOSEST(val, 625);

			val *= shunt_resistor;

			/* Overflow check: Assuming 32-bit val and shunt resistor, val <= 64bits */

			val = DIV_ROUND_CLOSEST_ULL(val, 625 * 1000);

			/* Overflow check: val is now <= 44 bits */

		} else {

			/*

			 * 0.5 mV * 25 uV = 0.0125 uV resolution.

			 * Divide first to avoid overflow;

			 * accept loss of accuracy.

			 */

			val = DIV_ROUND_CLOSEST(val, 25) * 2;

			/* 0.5 mV * 25 uV = 0.0125 uV resolution. */

			val *= shunt_resistor;

			/* Overflow check: Assuming 32-bit val and shunt resistor, val <= 64bits */

			val = DIV_ROUND_CLOSEST_ULL(val, 25 * 1000) * 2;

			/* Overflow check: val is now <= 51 bits */

		}

		break;

	case LTC2945_VIN_H:
@@ -193,7 +212,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, 
	case LTC2945_MAX_VIN_THRES_H:

	case LTC2945_MIN_VIN_THRES_H:

		/* 25 mV resolution. */

		val /= 25;

		val = DIV_ROUND_CLOSEST_ULL(val, 25);

		break;

	case LTC2945_ADIN_H:

	case LTC2945_MAX_ADIN_H:
@@ -208,14 +227,11 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, 
	case LTC2945_MIN_SENSE_H:

	case LTC2945_MAX_SENSE_THRES_H:

	case LTC2945_MIN_SENSE_THRES_H:

		/*

		 * 25 uV resolution. Convert to current as measured with

		 * an 1 mOhm sense resistor, in mA. If a different sense

		 * resistor is installed, calculate the actual current by

		 * dividing the reported current by the sense resistor value

		 * in mOhm.

		 */

		val = DIV_ROUND_CLOSEST(val, 25);

		/* 25 uV resolution. Convert to  mA. */

		val *= shunt_resistor;

		/* Overflow check: Assuming 32-bit val and 32-bit shunt resistor, val is 64bits */

		val = DIV_ROUND_CLOSEST_ULL(val, 25 * 1000);

		/* Overflow check: val is now <= 50 bits */

		break;

	default:

		return -EINVAL;
@@ -240,15 +256,16 @@ static ssize_t ltc2945_value_store(struct device *dev, 
				   const char *buf, size_t count)

{

	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);

	struct regmap *regmap = dev_get_drvdata(dev);

	struct ltc2945_data *data = dev_get_drvdata(dev);

	struct regmap *regmap = data->regmap;

	u8 reg = attr->index;

	unsigned long val;

	unsigned int val;

	u8 regbuf[3];

	int num_regs;

	int regval;

	long long regval;

	int ret;



	ret = kstrtoul(buf, 10, &val);

	ret = kstrtouint(buf, 10, &val);

	if (ret)

		return ret;
@@ -277,7 +294,8 @@ static ssize_t ltc2945_history_store(struct device *dev, 
				     const char *buf, size_t count)

{

	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);

	struct regmap *regmap = dev_get_drvdata(dev);

	struct ltc2945_data *data = dev_get_drvdata(dev);

	struct regmap *regmap = data->regmap;

	u8 reg = attr->index;

	int num_regs = is_power_reg(reg) ? 3 : 2;

	u8 buf_min[3] = { 0xff, 0xff, 0xff };
@@ -329,7 +347,8 @@ static ssize_t ltc2945_bool_show(struct device *dev, 
				 struct device_attribute *da, char *buf)

{

	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);

	struct regmap *regmap = dev_get_drvdata(dev);

	struct ltc2945_data *data = dev_get_drvdata(dev);

	struct regmap *regmap = data->regmap;

	unsigned int fault;

	int ret;
@@ -458,6 +477,12 @@ static int ltc2945_probe(struct i2c_client *client) 
	struct device *dev = &client->dev;

	struct device *hwmon_dev;

	struct regmap *regmap;

	struct ltc2945_data *data;



	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);

	if (!data)

		return -ENOMEM;

	dev_set_drvdata(dev, data);



	regmap = devm_regmap_init_i2c(client, &ltc2945_regmap_config);

	if (IS_ERR(regmap)) {
@@ -465,11 +490,19 @@ static int ltc2945_probe(struct i2c_client *client) 
		return PTR_ERR(regmap);

	}



	data->regmap = regmap;

	if (device_property_read_u32(dev, "shunt-resistor-micro-ohms",

				     &data->shunt_resistor))

		data->shunt_resistor = 1000;



	if (data->shunt_resistor == 0)

		return -EINVAL;



	/* Clear faults */

	regmap_write(regmap, LTC2945_FAULT, 0x00);



	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,

							   regmap,

							   data,

							   ltc2945_groups);

	return PTR_ERR_OR_ZERO(hwmon_dev);

}