drivers/hwmon/ina238.c

59  * based on a fixed shunt resistor value. This allows for conversion within the
61  * relative to the shunt resistor value within the driver. This is similar to
64  * The end result of this is that increasing shunt values (from a fixed 20 mOhm
65  * shunt) increase the effective current/power accuracy whilst limiting the
66  * range and decreasing shunt values decrease the effective accuracy but
70  *   Current (A) = (shunt voltage register * 5) * calibration / 81920
72  * The maximum shunt voltage is 163.835 mV (0x7fff, ADC_RANGE = 0, gain = 4).
73  * With the maximum current value of 0x7fff and a fixed shunt value results in
84  * to be scaled by the difference between the fixed shunt resistor and the
85  * actual shunt resistor:
87  *  shunt = 0x4000 / (819.2 * 10^6) / 0.001 = 20000 uOhms (with 1mA/lsb)
506 			   /* 0: shunt voltage */
511 			   /* 0: current through shunt */
555 	/* load shunt value */  in ina238_probe()
557 	if (device_property_read_u32(dev, "shunt-resistor", &data->rshunt) < 0 && pdata)  in ina238_probe()
560 		dev_err(dev, "invalid shunt resister value %u\n", data->rshunt);  in ina238_probe()
564 	/* load shunt gain value */  in ina238_probe()
565 	if (device_property_read_u32(dev, "ti,shunt-gain", &data->gain) < 0)  in ina238_probe()
568 		dev_err(dev, "invalid shunt gain value %u\n", data->gain);  in ina238_probe()