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hwmon: (ina2xx) Make calibration register value fixed 

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>
This commit is contained in:
Maciej Purski 2017-11-22 16:32:15 +01:00 committed by Guenter Roeck
parent cf583b4275
commit 5d389b1251
1 changed files with 50 additions and 37 deletions
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87
drivers/hwmon/ina2xx.c
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@ -95,18 +95,20 @@ 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;
@ -116,21 +118,21 @@ 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,
},
};
@ -169,12 +171,16 @@ static u16 ina226_interval_to_reg(int interval)
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);
}
/*
@ -187,10 +193,6 @@ static int ina2xx_init(struct ina2xx_data *data)
if (ret < 0)
return ret;
/*
* Set current LSB to 1mA, shunt is in uOhms
* (equation 13 in datasheet).
*/
return ina2xx_calibrate(data);
}
@ -268,15 +270,15 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg,
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 */
@ -304,9 +306,32 @@ static ssize_t ina2xx_show_value(struct device *dev,
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;
@ -316,18 +341,9 @@ static ssize_t ina2xx_set_shunt(struct device *dev,
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;
}
@ -387,7 +403,7 @@ static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ina2xx_show_value, NULL,
/* 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) */
@ -448,10 +464,7 @@ static int ina2xx_probe(struct i2c_client *client,
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;