[PATCH 2/2] hwmon: (ina2xx) Shift INA234 shunt and current registers

[Jonas Rebmann]

The INA219 has the lowest three bits of the bus voltage register
zero-reserved, the bus_voltage_shift ina2xx_config field was introduced
to accommodate for that.

The INA234 has four bits of the bus voltage, of the shunt voltage, and
of the current registers zero-reserved but the latter two were
implemented by choosing a 16x higher shunt_div instead of a separate
field specifying a bit shift.

This is possible because shunt voltage and current are divided by
shunt_div, hence a 16x higher shunt_div results in a 16x smaller LSB for
both the shunt voltage and the current register, perfectly accounting
for the missing bit shift.

For consistency and correctness, account for the reserved bits via
shunt_voltage_shift and current_shift configuration fields as already
done for voltage registers and use the conversion constants given in the
INA234 datasheet.

Signed-off-by: Jonas Rebmann <jre@xxxxxxxxxxxxxx>
---
 drivers/hwmon/ina2xx.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index 6a2cebbb9f15..613ffb622b7c 100644
--- a/drivers/hwmon/ina2xx.c
+++ b/drivers/hwmon/ina2xx.c
@@ -135,9 +135,11 @@ struct ina2xx_config {
 	bool has_update_interval;
 	int calibration_value;
 	int shunt_div;
+	int shunt_voltage_shift;
 	int bus_voltage_shift;
 	int bus_voltage_lsb;	/* uV */
 	int power_lsb_factor;
+	int current_shift;
 };
 
 struct ina2xx_data {
@@ -156,59 +158,69 @@ static const struct ina2xx_config ina2xx_config[] = {
 		.config_default = INA219_CONFIG_DEFAULT,
 		.calibration_value = 4096,
 		.shunt_div = 100,
+		.shunt_voltage_shift = 0,
 		.bus_voltage_shift = 3,
 		.bus_voltage_lsb = 4000,
 		.power_lsb_factor = 20,
 		.has_alerts = false,
 		.has_ishunt = false,
 		.has_power_average = false,
+		.current_shift = 0,
 		.has_update_interval = false,
 	},
 	[ina226] = {
 		.config_default = INA226_CONFIG_DEFAULT,
 		.calibration_value = 2048,
 		.shunt_div = 400,
+		.shunt_voltage_shift = 0,
 		.bus_voltage_shift = 0,
 		.bus_voltage_lsb = 1250,
 		.power_lsb_factor = 25,
 		.has_alerts = true,
 		.has_ishunt = false,
 		.has_power_average = false,
+		.current_shift = 0,
 		.has_update_interval = true,
 	},
 	[ina234] = {
 		.config_default = INA226_CONFIG_DEFAULT,
 		.calibration_value = 2048,
-		.shunt_div = 400, /* 2.5 µV/LSB raw ADC reading from INA2XX_SHUNT_VOLTAGE */
+		.shunt_div = 25, /* 2.5 µV/LSB raw ADC reading from INA2XX_SHUNT_VOLTAGE */
+		.shunt_voltage_shift = 4,
 		.bus_voltage_shift = 4,
 		.bus_voltage_lsb = 25600,
 		.power_lsb_factor = 32,
 		.has_alerts = true,
 		.has_ishunt = false,
 		.has_power_average = false,
+		.current_shift = 4,
 		.has_update_interval = true,
 	},
 	[ina260] = {
 		.config_default = INA260_CONFIG_DEFAULT,
 		.shunt_div = 400,
+		.shunt_voltage_shift = 0,
 		.bus_voltage_shift = 0,
 		.bus_voltage_lsb = 1250,
 		.power_lsb_factor = 8,
 		.has_alerts = true,
 		.has_ishunt = true,
 		.has_power_average = false,
+		.current_shift = 0,
 		.has_update_interval = true,
 	},
 	[sy24655] = {
 		.config_default = SY24655_CONFIG_DEFAULT,
 		.calibration_value = 4096,
 		.shunt_div = 400,
+		.shunt_voltage_shift = 0,
 		.bus_voltage_shift = 0,
 		.bus_voltage_lsb = 1250,
 		.power_lsb_factor = 25,
 		.has_alerts = true,
 		.has_ishunt = false,
 		.has_power_average = true,
+		.current_shift = 0,
 		.has_update_interval = false,
 	},
 };
@@ -262,7 +274,8 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg,
 	switch (reg) {
 	case INA2XX_SHUNT_VOLTAGE:
 		/* signed register */
-		val = DIV_ROUND_CLOSEST((s16)regval, data->config->shunt_div);
+		val = (s16)regval >> data->config->shunt_voltage_shift;
+		val = DIV_ROUND_CLOSEST(val, data->config->shunt_div);
 		break;
 	case INA2XX_BUS_VOLTAGE:
 		val = (regval >> data->config->bus_voltage_shift) *
@@ -274,7 +287,8 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg,
 		break;
 	case INA2XX_CURRENT:
 		/* signed register, result in mA */
-		val = (s16)regval * data->current_lsb_uA;
+		val = ((s16)regval >> data->config->current_shift) *
+		  data->current_lsb_uA;
 		val = DIV_ROUND_CLOSEST(val, 1000);
 		break;
 	case INA2XX_CALIBRATION:
@@ -368,6 +382,7 @@ static u16 ina226_alert_to_reg(struct ina2xx_data *data, int reg, long val)
 	case INA2XX_SHUNT_VOLTAGE:
 		val = clamp_val(val, 0, SHRT_MAX * data->config->shunt_div);
 		val *= data->config->shunt_div;
+		val <<= data->config->shunt_voltage_shift;
 		return clamp_val(val, 0, SHRT_MAX);
 	case INA2XX_BUS_VOLTAGE:
 		val = clamp_val(val, 0, 200000);
@@ -382,6 +397,7 @@ static u16 ina226_alert_to_reg(struct ina2xx_data *data, int reg, long val)
 		val = clamp_val(val, INT_MIN / 1000, INT_MAX / 1000);
 		/* signed register, result in mA */
 		val = DIV_ROUND_CLOSEST(val * 1000, data->current_lsb_uA);
+		val <<= data->config->current_shift;
 		return clamp_val(val, SHRT_MIN, SHRT_MAX);
 	default:
 		/* programmer goofed */

-- 
2.51.2.535.g419c72cb8a