hwmon: (ina2xx) Add support for current limits

While the chips supported by this driver do not directly support current
limits, they do support setting shunt voltage limits. The shunt voltage
divided by the shunt resistor value is the current. On top of that,
calibration values are set such that in the shunt voltage register and
the current register report the same values. That means we can report and
configure current limits based on shunt voltage limits, and we can do so
with much better accuracy than by setting shunt voltage limits.

Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/ina2xx.rst

@@ -99,6 +99,10 @@ Sysfs entries for ina226, ina230 and ina231 only
 ------------------------------------------------
 
 ======================= ====================================================
+curr1_lcrit		Critical low current
+curr1_crit		Critical high current
+curr1_lcrit_alarm	Current critical low alarm
+curr1_crit_alarm	Current critical high alarm
 in0_lcrit		Critical low shunt voltage
 in0_crit		Critical high shunt voltage
 in0_lcrit_alarm		Shunt voltage critical low alarm

drivers/hwmon/ina2xx.c

@@ -306,7 +306,7 @@ static int ina2xx_read_init(struct device *dev, int reg, long *val)
  * Turns alert limit values into register values.
  * Opposite of the formula in ina2xx_get_value().
  */
-static u16 ina226_alert_to_reg(struct ina2xx_data *data, int reg, unsigned long val)
+static u16 ina226_alert_to_reg(struct ina2xx_data *data, int reg, long val)
 {
 	switch (reg) {
 	case INA2XX_SHUNT_VOLTAGE:
@@ -322,6 +322,11 @@ static u16 ina226_alert_to_reg(struct ina2xx_data *data, int reg, unsigned long
 		val = clamp_val(val, 0, UINT_MAX - data->power_lsb_uW);
 		val = DIV_ROUND_CLOSEST(val, data->power_lsb_uW);
 		return clamp_val(val, 0, USHRT_MAX);
+	case INA2XX_CURRENT:
+		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);
+		return clamp_val(val, SHRT_MIN, SHRT_MAX);
 	default:
 		/* programmer goofed */
 		WARN_ON_ONCE(1);
@@ -473,9 +478,31 @@ static int ina2xx_power_read(struct device *dev, u32 attr, long *val)
 
 static int ina2xx_curr_read(struct device *dev, u32 attr, long *val)
 {
+	struct ina2xx_data *data = dev_get_drvdata(dev);
+	struct regmap *regmap = data->regmap;
+
+	/*
+	 * While the chips supported by this driver do not directly support
+	 * current limits, they do support setting shunt voltage limits.
+	 * The shunt voltage divided by the shunt resistor value is the current.
+	 * On top of that, calibration values are set such that in the shunt
+	 * voltage register and the current register report the same values.
+	 * That means we can report and configure current limits based on shunt
+	 * voltage limits.
+	 */
 	switch (attr) {
 	case hwmon_curr_input:
 		return ina2xx_read_init(dev, INA2XX_CURRENT, val);
+	case hwmon_curr_lcrit:
+		return ina226_alert_limit_read(data, INA226_SHUNT_UNDER_VOLTAGE_MASK,
+					       INA2XX_CURRENT, val);
+	case hwmon_curr_crit:
+		return ina226_alert_limit_read(data, INA226_SHUNT_OVER_VOLTAGE_MASK,
+					       INA2XX_CURRENT, val);
+	case hwmon_curr_lcrit_alarm:
+		return ina226_alert_read(regmap, INA226_SHUNT_UNDER_VOLTAGE_MASK, val);
+	case hwmon_curr_crit_alarm:
+		return ina226_alert_read(regmap, INA226_SHUNT_OVER_VOLTAGE_MASK, val);
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -547,6 +574,23 @@ static int ina2xx_power_write(struct device *dev, u32 attr, long val)
 	return 0;
 }
 
+static int ina2xx_curr_write(struct device *dev, u32 attr, long val)
+{
+	struct ina2xx_data *data = dev_get_drvdata(dev);
+
+	switch (attr) {
+	case hwmon_curr_lcrit:
+		return ina226_alert_limit_write(data, INA226_SHUNT_UNDER_VOLTAGE_MASK,
+						INA2XX_CURRENT, val);
+	case hwmon_curr_crit:
+		return ina226_alert_limit_write(data, INA226_SHUNT_OVER_VOLTAGE_MASK,
+						INA2XX_CURRENT, val);
+	default:
+		return -EOPNOTSUPP;
+	}
+	return 0;
+}
+
 static int ina2xx_write(struct device *dev, enum hwmon_sensor_types type,
 			u32 attr, int channel, long val)
 {
@@ -557,6 +601,8 @@ static int ina2xx_write(struct device *dev, enum hwmon_sensor_types type,
 		return ina2xx_in_write(dev, attr, channel, val);
 	case hwmon_power:
 		return ina2xx_power_write(dev, attr, val);
+	case hwmon_curr:
+		return ina2xx_curr_write(dev, attr, val);
 	default:
 		return -EOPNOTSUPP;
 	}
@@ -591,6 +637,16 @@ static umode_t ina2xx_is_visible(const void *_data, enum hwmon_sensor_types type
 		switch (attr) {
 		case hwmon_curr_input:
 			return 0444;
+		case hwmon_curr_lcrit:
+		case hwmon_curr_crit:
+			if (chip == ina226)
+				return 0644;
+			break;
+		case hwmon_curr_lcrit_alarm:
+		case hwmon_curr_crit_alarm:
+			if (chip == ina226)
+				return 0444;
+			break;
 		default:
 			break;
 		}
@@ -636,7 +692,8 @@ static const struct hwmon_channel_info * const ina2xx_info[] = {
 			   HWMON_I_INPUT | HWMON_I_CRIT | HWMON_I_CRIT_ALARM |
 			   HWMON_I_LCRIT | HWMON_I_LCRIT_ALARM
 			   ),
-	HWMON_CHANNEL_INFO(curr, HWMON_C_INPUT),
+	HWMON_CHANNEL_INFO(curr, HWMON_C_INPUT | HWMON_C_CRIT | HWMON_C_CRIT_ALARM |
+			   HWMON_C_LCRIT | HWMON_C_LCRIT_ALARM),
 	HWMON_CHANNEL_INFO(power,
 			   HWMON_P_INPUT | HWMON_P_CRIT | HWMON_P_CRIT_ALARM),
 	NULL