hwmon: (ina3221) Implement ti,single-shot DT property

By default, ina3221, as a hardware monitor, continuously measures
the inputs and generates corresponding data. However, for battery
powered devices, this mode might be power consuming.

The DT binding doc is updated with a new boolean type property to
allow changing the default operating mode from consuming mode to
single-shot mode, which will measure input on demand and then shut
down to save power.

So this patch implements the DT property accordingly.
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/ina3221.c

@@ -111,6 +111,7 @@ struct ina3221_input {
  * @inputs: Array of channel input source specific structures
  * @lock: mutex lock to serialize sysfs attribute accesses
  * @reg_config: Register value of INA3221_CONFIG
+ * @single_shot: running in single-shot operating mode
  */
 struct ina3221_data {
 	struct device *pm_dev;
@@ -119,6 +120,8 @@ struct ina3221_data {
 	struct ina3221_input inputs[INA3221_NUM_CHANNELS];
 	struct mutex lock;
 	u32 reg_config;
+
+	bool single_shot;
 };
 
 static inline bool ina3221_is_enabled(struct ina3221_data *ina, int channel)
@@ -188,6 +191,11 @@ static int ina3221_read_in(struct device *dev, u32 attr, int channel, long *val)
 		if (!ina3221_is_enabled(ina, channel))
 			return -ENODATA;
 
+		/* Write CONFIG register to trigger a single-shot measurement */
+		if (ina->single_shot)
+			regmap_write(ina->regmap, INA3221_CONFIG,
+				     ina->reg_config);
+
 		ret = ina3221_wait_for_data(ina);
 		if (ret)
 			return ret;
@@ -232,6 +240,11 @@ static int ina3221_read_curr(struct device *dev, u32 attr,
 		if (!ina3221_is_enabled(ina, channel))
 			return -ENODATA;
 
+		/* Write CONFIG register to trigger a single-shot measurement */
+		if (ina->single_shot)
+			regmap_write(ina->regmap, INA3221_CONFIG,
+				     ina->reg_config);
+
 		ret = ina3221_wait_for_data(ina);
 		if (ret)
 			return ret;
@@ -614,6 +627,8 @@ static int ina3221_probe_from_dt(struct device *dev, struct ina3221_data *ina)
 	if (!np)
 		return 0;
 
+	ina->single_shot = of_property_read_bool(np, "ti,single-shot");
+
 	for_each_child_of_node(np, child) {
 		ret = ina3221_probe_child_from_dt(dev, child, ina);
 		if (ret)
@@ -663,6 +678,10 @@ static int ina3221_probe(struct i2c_client *client,
 	/* The driver will be reset, so use reset value */
 	ina->reg_config = INA3221_CONFIG_DEFAULT;
 
+	/* Clear continuous bit to use single-shot mode */
+	if (ina->single_shot)
+		ina->reg_config &= ~INA3221_CONFIG_MODE_CONTINUOUS;
+
 	/* Disable channels if their inputs are disconnected */
 	for (i = 0; i < INA3221_NUM_CHANNELS; i++) {
 		if (ina->inputs[i].disconnected)