| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20171217124837.71ce745a@archlinux>
Date: Sun, 17 Dec 2017 12:48:37 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Maciej Purski <m.purski@...sung.com>
Cc: Stefan Bruens <stefan.bruens@...h-aachen.de>,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-hwmon@...r.kernel.org,
Peter Meerwald-Stadler <pmeerw@...erw.net>,
Lars-Peter Clausen <lars@...afoo.de>,
Hartmut Knaack <knaack.h@....de>,
Jean Delvare <jdelvare@...e.com>,
Guenter Roeck <linux@...ck-us.net>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v3] iio: adc: ina2xx: Make calibration register value
fixed
On Fri, 15 Dec 2017 08:59:23 +0100
Maciej Purski <m.purski@...sung.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@...sung.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;
> }
>
Powered by blists - more mailing lists