This is a note to let you know that I've just added the patch titled
hwmon: (ina2xx) Make calibration register value fixed
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: hwmon-ina2xx-make-calibration-register-value-fixed.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Mon Apr 9 17:09:24 CEST 2018
From: Maciej Purski m.purski@samsung.com Date: Wed, 22 Nov 2017 16:32:15 +0100 Subject: hwmon: (ina2xx) Make calibration register value fixed
From: Maciej Purski m.purski@samsung.com
[ Upstream commit 5d389b125186cf254ad5b8015763ac07c151aea4 ]
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)
Signed-off-by: Maciej Purski m.purski@samsung.com Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/hwmon/ina2xx.c | 87 ++++++++++++++++++++++++++++--------------------- 1 file changed, 50 insertions(+), 37 deletions(-)
--- a/drivers/hwmon/ina2xx.c +++ b/drivers/hwmon/ina2xx.c @@ -94,18 +94,20 @@ enum ina2xx_ids { ina219, ina226 };
struct ina2xx_config { u16 config_default; - int calibration_factor; + int calibration_value; int registers; int shunt_div; int bus_voltage_shift; int bus_voltage_lsb; /* uV */ - int power_lsb; /* uW */ + int power_lsb_factor; };
struct ina2xx_data { const struct ina2xx_config *config;
long rshunt; + long current_lsb_uA; + long power_lsb_uW; struct mutex config_lock; struct regmap *regmap;
@@ -115,21 +117,21 @@ struct ina2xx_data { static const struct ina2xx_config ina2xx_config[] = { [ina219] = { .config_default = INA219_CONFIG_DEFAULT, - .calibration_factor = 40960000, + .calibration_value = 4096, .registers = INA219_REGISTERS, .shunt_div = 100, .bus_voltage_shift = 3, .bus_voltage_lsb = 4000, - .power_lsb = 20000, + .power_lsb_factor = 20, }, [ina226] = { .config_default = INA226_CONFIG_DEFAULT, - .calibration_factor = 5120000, + .calibration_value = 2048, .registers = INA226_REGISTERS, .shunt_div = 400, .bus_voltage_shift = 0, .bus_voltage_lsb = 1250, - .power_lsb = 25000, + .power_lsb_factor = 25, }, };
@@ -168,12 +170,16 @@ static u16 ina226_interval_to_reg(int in return INA226_SHIFT_AVG(avg_bits); }
+/* + * Calibration register is set to the best value, which eliminates + * truncation errors on calculating current register in hardware. + * According to datasheet (eq. 3) the best values are 2048 for + * ina226 and 4096 for ina219. They are hardcoded as calibration_value. + */ static int ina2xx_calibrate(struct ina2xx_data *data) { - u16 val = DIV_ROUND_CLOSEST(data->config->calibration_factor, - data->rshunt); - - return regmap_write(data->regmap, INA2XX_CALIBRATION, val); + return regmap_write(data->regmap, INA2XX_CALIBRATION, + data->config->calibration_value); }
/* @@ -186,10 +192,6 @@ static int ina2xx_init(struct ina2xx_dat if (ret < 0) return ret;
- /* - * Set current LSB to 1mA, shunt is in uOhms - * (equation 13 in datasheet). - */ return ina2xx_calibrate(data); }
@@ -267,15 +269,15 @@ static int ina2xx_get_value(struct ina2x val = DIV_ROUND_CLOSEST(val, 1000); break; case INA2XX_POWER: - val = regval * data->config->power_lsb; + val = regval * data->power_lsb_uW; break; case INA2XX_CURRENT: - /* signed register, LSB=1mA (selected), in mA */ - val = (s16)regval; + /* signed register, result in mA */ + val = regval * data->current_lsb_uA; + val = DIV_ROUND_CLOSEST(val, 1000); break; case INA2XX_CALIBRATION: - val = DIV_ROUND_CLOSEST(data->config->calibration_factor, - regval); + val = regval; break; default: /* programmer goofed */ @@ -303,9 +305,32 @@ static ssize_t ina2xx_show_value(struct ina2xx_get_value(data, attr->index, regval)); }
-static ssize_t ina2xx_set_shunt(struct device *dev, - struct device_attribute *da, - const char *buf, size_t count) +/* + * In order to keep calibration register value fixed, the product + * of current_lsb and shunt_resistor should also be fixed and equal + * to shunt_voltage_lsb = 1 / shunt_div multiplied by 10^9 in order + * to keep the scale. + */ +static int ina2xx_set_shunt(struct ina2xx_data *data, long val) +{ + unsigned int dividend = DIV_ROUND_CLOSEST(1000000000, + data->config->shunt_div); + if (val <= 0 || val > dividend) + return -EINVAL; + + mutex_lock(&data->config_lock); + data->rshunt = val; + data->current_lsb_uA = DIV_ROUND_CLOSEST(dividend, val); + data->power_lsb_uW = data->config->power_lsb_factor * + data->current_lsb_uA; + mutex_unlock(&data->config_lock); + + return 0; +} + +static ssize_t ina2xx_store_shunt(struct device *dev, + struct device_attribute *da, + const char *buf, size_t count) { unsigned long val; int status; @@ -315,18 +340,9 @@ static ssize_t ina2xx_set_shunt(struct d if (status < 0) return status;
- if (val == 0 || - /* Values greater than the calibration factor make no sense. */ - val > data->config->calibration_factor) - return -EINVAL; - - mutex_lock(&data->config_lock); - data->rshunt = val; - status = ina2xx_calibrate(data); - mutex_unlock(&data->config_lock); + status = ina2xx_set_shunt(data, val); if (status < 0) return status; - return count; }
@@ -386,7 +402,7 @@ static SENSOR_DEVICE_ATTR(power1_input,
/* shunt resistance */ static SENSOR_DEVICE_ATTR(shunt_resistor, S_IRUGO | S_IWUSR, - ina2xx_show_value, ina2xx_set_shunt, + ina2xx_show_value, ina2xx_store_shunt, INA2XX_CALIBRATION);
/* update interval (ina226 only) */ @@ -441,10 +457,7 @@ static int ina2xx_probe(struct i2c_clien val = INA2XX_RSHUNT_DEFAULT; }
- if (val <= 0 || val > data->config->calibration_factor) - return -ENODEV; - - data->rshunt = val; + ina2xx_set_shunt(data, val);
ina2xx_regmap_config.max_register = data->config->registers;
Patches currently in stable-queue which might be from m.purski@samsung.com are
queue-4.9/hwmon-ina2xx-make-calibration-register-value-fixed.patch