Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751517AbdL2RcP convert rfc822-to-8bit (ORCPT ); Fri, 29 Dec 2017 12:32:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:55480 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751107AbdL2RcM (ORCPT ); Fri, 29 Dec 2017 12:32:12 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E6E512197D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jic23@kernel.org Date: Fri, 29 Dec 2017 17:32:07 +0000 From: Jonathan Cameron To: Stefan =?UTF-8?B?QnLDvG5z?= Cc: Maciej Purski , , , , "Peter Meerwald-Stadler" , Lars-Peter Clausen , Hartmut Knaack , Jean Delvare , "Guenter Roeck" , Marek Szyprowski , Bartlomiej Zolnierkiewicz Subject: Re: [PATCH v4] iio: adc: ina2xx: Make calibration register value fixed Message-ID: <20171229173207.32cfbc76@archlinux> In-Reply-To: <5526600.j0ivttN8ph@bacchus.fritz.box> References: <1513586638-6036-1-git-send-email-m.purski@samsung.com> <5526600.j0ivttN8ph@bacchus.fritz.box> X-Mailer: Claws Mail 3.15.1-dirty (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6057 Lines: 175 On Mon, 18 Dec 2017 10:02:44 +0100 Stefan Brüns wrote: > 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 > > Reviewed-by: Stefan Brüns Applied to the togreg branch of iio.git and pushed out ass testing for the autobuilders to play with it. Thanks, Jonathan > > > --- > > 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; > > } > >