hwmon: (tps23861) set current shunt value

TPS23861 has a configuration bit for setting of the
current shunt value used on the board.
Its bit 0 of the General Mask 1 register.

According to the datasheet bit values are:
0 for 255 mOhm (Default)
1 for 250 mOhm

So, configure the bit before registering the hwmon
device according to the value passed in the DTS or
default one if none is passed.

This caused potentially reading slightly skewed values
due to max current value being 1.02A when 250mOhm shunt
is used instead of 1.0A when 255mOhm is used.

Fixes: fff7b8a ("hwmon: add Texas Instruments TPS23861 driver")
Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Link: https://lore.kernel.org/r/20210609220728.499879-2-robert.marko@sartura.hr
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/tps23861.c

@@ -99,6 +99,9 @@
 #define POWER_ENABLE			0x19
 #define TPS23861_NUM_PORTS		4
 
+#define TPS23861_GENERAL_MASK_1		0x17
+#define TPS23861_CURRENT_SHUNT_MASK	BIT(0)
+
 #define TEMPERATURE_LSB			652 /* 0.652 degrees Celsius */
 #define VOLTAGE_LSB			3662 /* 3.662 mV */
 #define SHUNT_RESISTOR_DEFAULT		255000 /* 255 mOhm */
@@ -561,6 +564,15 @@ static int tps23861_probe(struct i2c_client *client)
 	else
 		data->shunt_resistor = SHUNT_RESISTOR_DEFAULT;
 
+	if (data->shunt_resistor == SHUNT_RESISTOR_DEFAULT)
+		regmap_clear_bits(data->regmap,
+				  TPS23861_GENERAL_MASK_1,
+				  TPS23861_CURRENT_SHUNT_MASK);
+	else
+		regmap_set_bits(data->regmap,
+				TPS23861_GENERAL_MASK_1,
+				TPS23861_CURRENT_SHUNT_MASK);
+
 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
 							 data, &tps23861_chip_info,
 							 NULL);