hwmon: (ina2xx) Add device tree support to pass alert polarity

The INA230 has an Alert pin which is asserted when the alert
function selected in the Mask/Enable register exceeds the
value programmed into the Alert Limit register. Assertion is based
on the Alert Polarity Bit (APOL, bit 1 of the Mask/Enable register).
It is default set to value 0 i.e Normal (active-low open collector).
However, hardware can be designed in such a way that expects Alert pin
to become active high if a user-defined threshold in Alert limit
register has been exceeded. This patch adds a way to pass alert polarity
value to the driver via device tree.

Signed-off-by: Amna Waseem <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/hwmon/ina2xx.c

···
 #define INA226_READ_AVG(reg)		(((reg) & INA226_AVG_RD_MASK) >> 9)
 #define INA226_SHIFT_AVG(val)		((val) << 9)
 
+#define INA226_ALERT_POLARITY_MASK		0x0002
+#define INA226_SHIFT_ALERT_POLARITY(val)	((val) << 1)
+#define INA226_ALERT_POL_LOW			0
+#define INA226_ALERT_POL_HIGH			1
+
 /* bit number of alert functions in Mask/Enable Register */
 #define INA226_SHUNT_OVER_VOLTAGE_BIT	15
 #define INA226_SHUNT_UNDER_VOLTAGE_BIT	14
···
 				ARRAY_SIZE(ina226_avg_tab));
 
 	return INA226_SHIFT_AVG(avg_bits);
+}
+
+static int ina2xx_set_alert_polarity(struct ina2xx_data *data,
+				     unsigned long val)
+{
+	return regmap_update_bits(data->regmap, INA226_MASK_ENABLE,
+				 INA226_ALERT_POLARITY_MASK,
+				 INA226_SHIFT_ALERT_POLARITY(val));
 }
 
 /*
···
 	ret = devm_regulator_get_enable(dev, "vs");
 	if (ret)
 		return dev_err_probe(dev, ret, "failed to enable vs regulator\n");
+
+	if (chip == ina226) {
+		if (of_property_read_bool(dev->of_node, "ti,alert-polarity-active-high")) {
+			ret = ina2xx_set_alert_polarity(data,
+							INA226_ALERT_POL_HIGH);
+			if (ret < 0) {
+				return dev_err_probe(dev, ret,
+					"failed to set alert polarity active high\n");
+			}
+		} else {
+			/* Set default value i.e active low */
+			ret = ina2xx_set_alert_polarity(data,
+							INA226_ALERT_POL_LOW);
+			if (ret < 0) {
+				return dev_err_probe(dev, ret,
+					"failed to set alert polarity active low\n");
+			}
+		}
+	}
 
 	ret = ina2xx_init(data);
 	if (ret < 0) {