On Monday, December 18, 2017 9:43:58 AM CET Maciej Purski wrote: > 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: Maciej Purski <m.purski@xxxxxxxxxxx> Reviewed-by: Stefan Brüns <stefan.bruens@xxxxxxxxxxxxxx> > --- > Changes in v4: > - fix comments > > Changes in v3: > - remove variable current_lsb and calculate it on each read of current > and power scale value > - update comments > > Changes in v2: > - rebase on top of the latest next > - remove a redundant variable - power_lsb_uW > - fix comments > --- > drivers/iio/adc/ina2xx-adc.c | 64 > +++++++++++++++++++++++--------------------- 1 file changed, 33 > insertions(+), 31 deletions(-) > > diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c > index ddf8781..9e8ca12 100644 > --- a/drivers/iio/adc/ina2xx-adc.c > +++ b/drivers/iio/adc/ina2xx-adc.c > @@ -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; > } -- Stefan Brüns / Bergstraße 21 / 52062 Aachen phone: +49 241 53809034 mobile: +49 151 50412019 -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
