| Message ID | 1513324763-21541-1-git-send-email-m.purski@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, 15 Dec 2017 08:59:23 +0100 Maciej Purski <m.purski@samsung.com> 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@samsung.com> Looks good to me. I'll let it sit for Stefan to have a change to look at it though. If it looks like I've forgotten it by early Jan do give me a kick. Thanks, Jonathan > > --- > 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 | 56 +++++++++++++++++++++----------------------- > 1 file changed, 27 insertions(+), 29 deletions(-) > > diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c > index ddf8781..3488100 100644 > --- a/drivers/iio/adc/ina2xx-adc.c > +++ b/drivers/iio/adc/ina2xx-adc.c > @@ -124,11 +124,11 @@ 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 */ > + int power_lsb_factor; > enum ina2xx_ids chip_id; > }; > > @@ -149,20 +149,20 @@ 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, > }, > }; > @@ -228,15 +228,17 @@ static int ina2xx_read_raw(struct iio_dev *indio_dev, > return IIO_VAL_FRACTIONAL; > > case INA2XX_POWER: > - /* processed (mW) = raw*lsb (uW) / 1000 */ > - *val = chip->config->power_lsb; > - *val2 = 1000; > + /* processed (mW) = raw * factor * current_lsb (mW)*/ > + *val = chip->config->power_lsb_factor * > + 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; > + /* processed (mA) = raw * lsb ([nV] / [uOhm] = [mA]) */ > + *val = chip->config->shunt_voltage_lsb; > + *val2 = chip->shunt_resistor_uohm; > + return IIO_VAL_FRACTIONAL; > } > > case IIO_CHAN_INFO_HARDWAREGAIN: > @@ -541,25 +543,26 @@ 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); > } > > +/* > + * As the calibration register is fixed, the product of current_lsb > + * and shunt_resistor should also be fixed and equal > + * to shunt_voltage_lsb. Current_lsb will be calculated in read_raw() > + */ > 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 +595,6 @@ 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; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Friday, December 15, 2017 8:59:23 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@samsung.com> The code itself looks fine now, although I have some nitpicks regarding the comments, see below. Regards, Stefan > --- > 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 | 56 > +++++++++++++++++++++----------------------- 1 file changed, 27 > insertions(+), 29 deletions(-) > > diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c > index ddf8781..3488100 100644 > --- a/drivers/iio/adc/ina2xx-adc.c > +++ b/drivers/iio/adc/ina2xx-adc.c > @@ -124,11 +124,11 @@ 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 */ > + int power_lsb_factor; A comment for the power_lsb_factor would be nice, something like /* fixed relation between current and power lsb, uW/uA */ > enum ina2xx_ids chip_id; > }; > > @@ -149,20 +149,20 @@ 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, > }, > }; > @@ -228,15 +228,17 @@ static int ina2xx_read_raw(struct iio_dev *indio_dev, > return IIO_VAL_FRACTIONAL; > > case INA2XX_POWER: > - /* processed (mW) = raw*lsb (uW) / 1000 */ > - *val = chip->config->power_lsb; > - *val2 = 1000; > + /* processed (mW) = raw * factor * current_lsb (mW)*/ > + *val = chip->config->power_lsb_factor * > + 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; > + /* processed (mA) = raw * lsb ([nV] / [uOhm] = [mA]) */ > + *val = chip->config->shunt_voltage_lsb; > + *val2 = chip->shunt_resistor_uohm; > + return IIO_VAL_FRACTIONAL; > } It think this may be somewhat easier to follow if you place the CURRENT case above the POWER case, and then extend the comments for both cases, e.g.: /* * processed (mA) = raw * current_lsb (mA) * current_lsb (mA) = shunt_voltage_lsb (nV) / shunt_resistor (uOhm) */ and /* * processed (mW) = raw * power_lsb (mW) * power_lsb (mW) = power_lsb_factor (mW/mA) * current_lsb (mA) */ > case IIO_CHAN_INFO_HARDWAREGAIN: > @@ -541,25 +543,26 @@ 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); > } > > +/* > + * As the calibration register is fixed, the product of current_lsb > + * and shunt_resistor should also be fixed and equal > + * to shunt_voltage_lsb. Current_lsb will be calculated in read_raw() > + */ I think this comment is misplaced here. Neither current_lsb nor shunt_voltage_lsb are used in the remaining code, the resistor value is just stored. > 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 +595,6 @@ 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; > }
diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c index ddf8781..3488100 100644 --- a/drivers/iio/adc/ina2xx-adc.c +++ b/drivers/iio/adc/ina2xx-adc.c @@ -124,11 +124,11 @@ 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 */ + int power_lsb_factor; enum ina2xx_ids chip_id; }; @@ -149,20 +149,20 @@ 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, }, }; @@ -228,15 +228,17 @@ static int ina2xx_read_raw(struct iio_dev *indio_dev, return IIO_VAL_FRACTIONAL; case INA2XX_POWER: - /* processed (mW) = raw*lsb (uW) / 1000 */ - *val = chip->config->power_lsb; - *val2 = 1000; + /* processed (mW) = raw * factor * current_lsb (mW)*/ + *val = chip->config->power_lsb_factor * + 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; + /* processed (mA) = raw * lsb ([nV] / [uOhm] = [mA]) */ + *val = chip->config->shunt_voltage_lsb; + *val2 = chip->shunt_resistor_uohm; + return IIO_VAL_FRACTIONAL; } case IIO_CHAN_INFO_HARDWAREGAIN: @@ -541,25 +543,26 @@ 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); } +/* + * As the calibration register is fixed, the product of current_lsb + * and shunt_resistor should also be fixed and equal + * to shunt_voltage_lsb. Current_lsb will be calculated in read_raw() + */ 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 +595,6 @@ 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; }
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@samsung.com> --- 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 | 56 +++++++++++++++++++++----------------------- 1 file changed, 27 insertions(+), 29 deletions(-)