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Commit a28caa7b authored by Maciej Purski's avatar Maciej Purski Committed by Greg Kroah-Hartman
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iio: adc: ina2xx: Make calibration register value fixed 

Calibration register is used for calculating current register in
hardware according to datasheet:
current = shunt_volt * calib_register / 2048 (ina 226)
current = shunt_volt * calib_register / 4096 (ina 219)

Fix calib_register value to 2048 for ina226 and 4096 for ina 219 in
order to avoid truncation error and provide best precision allowed
by shunt_voltage measurement. Make current scale value follow changes
of shunt_resistor from sysfs as calib_register value is now fixed.

Power_lsb value should also follow shunt_resistor changes as stated in
datasheet:
power_lsb = 25 * current_lsb (ina 226)
power_lsb = 20 * current_lsb (ina 219)

This is a part of the patchset: https://lkml.org/lkml/2017/11/22/394



Signed-off-by: default avatarMaciej Purski <m.purski@samsung.com>
Reviewed-by: default avatarStefan Brüns <stefan.bruens@rwth-aachen.de>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bbdcbd12

drivers/iio/adc/ina2xx-adc.c

+33 −31
Original line number Diff line number Diff line
@@ -124,11 +124,12 @@ enum ina2xx_ids { ina219, ina226 }; 


struct ina2xx_config {

	u16 config_default;

	int calibration_factor;

	int calibration_value;

	int shunt_voltage_lsb;	/* nV */

	int bus_voltage_shift;	/* position of lsb */

	int bus_voltage_lsb;	/* uV */

	int power_lsb;		/* uW */

	/* fixed relation between current and power lsb, uW/uA */

	int power_lsb_factor;

	enum ina2xx_ids chip_id;

};
@@ -149,20 +150,20 @@ struct ina2xx_chip_info { 
static const struct ina2xx_config ina2xx_config[] = {

	[ina219] = {

		.config_default = INA219_CONFIG_DEFAULT,

		.calibration_factor = 40960000,

		.calibration_value = 4096,

		.shunt_voltage_lsb = 10000,

		.bus_voltage_shift = INA219_BUS_VOLTAGE_SHIFT,

		.bus_voltage_lsb = 4000,

		.power_lsb = 20000,

		.power_lsb_factor = 20,

		.chip_id = ina219,

	},

	[ina226] = {

		.config_default = INA226_CONFIG_DEFAULT,

		.calibration_factor = 5120000,

		.calibration_value = 2048,

		.shunt_voltage_lsb = 2500,

		.bus_voltage_shift = 0,

		.bus_voltage_lsb = 1250,

		.power_lsb = 25000,

		.power_lsb_factor = 25,

		.chip_id = ina226,

	},

};
@@ -227,16 +228,26 @@ static int ina2xx_read_raw(struct iio_dev *indio_dev, 
			*val2 = 1000;

			return IIO_VAL_FRACTIONAL;



		case INA2XX_POWER:

			/* processed (mW) = raw*lsb (uW) / 1000 */

			*val = chip->config->power_lsb;

			*val2 = 1000;

		case INA2XX_CURRENT:

			/*

			 * processed (mA) = raw * current_lsb (mA)

			 * current_lsb (mA) = shunt_voltage_lsb (nV) /

			 *                    shunt_resistor (uOhm)

			 */

			*val = chip->config->shunt_voltage_lsb;

			*val2 = chip->shunt_resistor_uohm;

			return IIO_VAL_FRACTIONAL;



		case INA2XX_CURRENT:

			/* processed (mA) = raw (mA) */

			*val = 1;

			return IIO_VAL_INT;

		case INA2XX_POWER:

			/*

			 * processed (mW) = raw * power_lsb (mW)

			 * power_lsb (mW) = power_lsb_factor (mW/mA) *

			 *                  current_lsb (mA)

			 */

			*val = chip->config->power_lsb_factor *

			       chip->config->shunt_voltage_lsb;

			*val2 = chip->shunt_resistor_uohm;

			return IIO_VAL_FRACTIONAL;

		}



	case IIO_CHAN_INFO_HARDWAREGAIN:
@@ -541,25 +552,21 @@ static ssize_t ina2xx_allow_async_readout_store(struct device *dev, 
}



/*

 * Set current LSB to 1mA, shunt is in uOhms

 * (equation 13 in datasheet). We hardcode a Current_LSB

 * of 1.0 x10-3. The only remaining parameter is RShunt.

 * There is no need to expose the CALIBRATION register

 * to the user for now. But we need to reset this register

 * if the user updates RShunt after driver init, e.g upon

 * reading an EEPROM/Probe-type value.

 * Calibration register is set to the best value, which eliminates

 * truncation errors on calculating current register in hardware.

 * According to datasheet (INA 226: eq. 3, INA219: eq. 4) the best values

 * are 2048 for ina226 and 4096 for ina219. They are hardcoded as

 * calibration_value.

 */

static int ina2xx_set_calibration(struct ina2xx_chip_info *chip)

{

	u16 regval = DIV_ROUND_CLOSEST(chip->config->calibration_factor,

				   chip->shunt_resistor_uohm);



	return regmap_write(chip->regmap, INA2XX_CALIBRATION, regval);

	return regmap_write(chip->regmap, INA2XX_CALIBRATION,

			    chip->config->calibration_value);

}



static int set_shunt_resistor(struct ina2xx_chip_info *chip, unsigned int val)

{

	if (val <= 0 || val > chip->config->calibration_factor)

	if (val == 0 || val > INT_MAX)

		return -EINVAL;



	chip->shunt_resistor_uohm = val;
@@ -592,11 +599,6 @@ static ssize_t ina2xx_shunt_resistor_store(struct device *dev, 
	if (ret)

		return ret;



	/* Update the Calibration register */

	ret = ina2xx_set_calibration(chip);

	if (ret)

		return ret;



	return len;

}