[PATCH v4 2/2] hwmon: (ina2xx) Add device tree support to pass alert polarity

[Amna Waseem <Amna.Waseem@axis.com>]

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 <Amna.Waseem@axis.com>
---
 drivers/hwmon/ina2xx.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index d8415d1f21fc..f26ba479bf5c 100644
--- a/drivers/hwmon/ina2xx.c
+++ b/drivers/hwmon/ina2xx.c
@@ -73,6 +73,11 @@
 #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
@@ -178,6 +183,14 @@ static u16 ina226_interval_to_reg(int interval)
 	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));
+}
+
 /*
  * Calibration register is set to the best value, which eliminates
  * truncation errors on calculating current register in hardware.
@@ -659,6 +672,25 @@ static int ina2xx_probe(struct i2c_client *client)
 	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) {
 		dev_err(dev, "error configuring the device: %d\n", ret);

-- 
2.30.2